1

2

3

TUNING STANDARD TRIUMPHSOVER 1300 cc

MOTOBOOKSPORTPEEDS

David Vizard

4

(c) Copyright 1970 by Speed and Sports Publications Ltd. All rights reserved.

FIRST IMPRESSION FEBRUARY 1970

85113-029-1

Printed and Published by

SPEED AND SPORTS PUBLICATIONS LTD

Acorn House Victoria Road Acton London W.3.

5

INTRODUCTION 7chapter 1OVERHAULING THE SIX CYLINDER ENGINE 11chapter 2IMPROVING THE LUBRICATION 21chapter 3BOTTOM END PREPARATION 25chapter 4MODIFYING THE EARLY 6 CYLINDER HEAD 33chapter 5BIGGER VALVES FOR EARLY HEADS 47chapter 6MODIFYING THE LATER 2000 AND 2500 cc HEADS 53chapter 7MODIFYING THE TR4 HEAD 63chapter 8THE ULTIMATE HEAD 69chapter 9PORT MATCHING AND DOWELLING 75chapter 10SPRINGS ROCKERS PUSHRODS AND TAPPETS 77chapter 11ENGINE INTERCHANGEABILITY 81chapter 12STRENGTHENING THE BOTTOM END FOR COMPETITION 85chapter 13LIGHTENING ENGINE COMPONENTS 89chapter 14HIGH PERFORMANCE CAMS 95chapter 15CARBURATION FUEL INJECTION AND MANIFOLDING 105chapter 16ASSESSING THE RESULTS 109chapter 17THE TRANSMISSIONS 111chapter 18SUSPENSIONS AND BRAKES 137chapter 19BODYWORK MODIFICATIONS 153

contentspage

6

7

IT would appear that over the lastdecade, Triumph’s policy has been tointroduce a car of a basically moderndesign-and, over a period, develop itto suit various markets. This policyhas been adopted in preference to themore normal method of introducingan entirely new car for a given mar-ket.

Up to a point, this type of thinkingmust be commended. Since the ma-jority of Triumphs are endowed witha respectable level of roadholding andbraking power, the only items whichbecome vastly changeable are thepower units and transmissions. Sincethe non-sporting driver is unlikely tocomplain if the car has a far higherlevel of roadholding than he is everlikely to use, the manufacturers have,in effect, killed two birds with onestone. The two birds in question are,of course, the sporting and thenonsporting type of driver.

There is inevitably a disadvantagewhen going about things in this man-ner, and this can be easily summedup as a weight penalty. If we design acar in which a range of engines are to

INTRODUCTIONbe used, ones, that is, which vary con-siderably in size, weight and poweroutput, we must build the rolling chas-sis to cater for the most powerful en-gine it is likely to have fitted. Thismeans the car can be a little over-weight for the smaller engines, thusresulting in a more sluggish car thanis really desirable.

For an example, to take the Her-ald/Vitesse range of Triumph cars.The early Herald with its 948 c.c. en-gine and an all up weight of around17 cwts. could hardly be consideredthe spriteliest of machines, rather itshould be considered to be the heavy-weight amongst 1 -litre vehicles. Withthe introduction of the 1200 the weightto capacity situation improved but wasstill not altogether remedied. Whenthe 1600 Vitesse came along thingstook a turn for the better. Here we hada car which was not unduly heavy forits 1 1/2litre power plant. Not only didthe car have-a good weight to capac-ity ratio, but also an engine whoseoutput could be substantially raisedto produce a relatively quick machine.But for competition purposes the 1600

8

Vitesse still lacked the edge neededto make it a successful race machine.When the capacity of the Vitesse wasincreased to 2-litres and the G.T.6was introduced, one would have ex-pected the competition scene tochange substantially. It would nothave been unreasonable to supposethat these two cars would have domi-nated the competition in their respec-tive classes, but this has not been thecase. Half the reason for this couldbe that old ideas die hard. The thoughtof one of Triumph’s products sweep-ing the field and making hay with therest of the competition may not yethave caught on. The idea that it couldbe possible and that they should doso is not altogether unreasonable.

Let us look at the situation in ananalytical fashion and compare, say,the 2-litre Vitesse with some of itssuccessful competition rivals pro-duced by other manufacturers. Forour purposes a good comparisonwould be to see if we can achieve amachine with a similar performanceto an F.V.A. engined 2-litre Escort. Ifthis can be done, then without ashadow of doubt we can say a Vitessecan be competitive.

The F.V.A. Escort has a 2-litre en-gine producing a power output in theorder of 220 b.h.p. The overall weightready to race is about 15% cwt. andsuspension is independent at the frontbut not so at the rear. The rear endon these cars is served by an ex-tremely well located live axle. Howwould our hypothetical race preparedVitesse compare with this ? First off,we should find it very difficult to matchor even approach the power outputof the F.V.A. engine without resortingto very expensive twin overhead camheads. Tuning Std Triumphs over1300c.c. This inevitably limits the

number of us who could entertain thefeasability of such a project down toa very small minority. Our best plan isto ignore such a scheme and stickwith the more conventional pushrodlayout. If we really went to town withdown draft heads, fuel injection, etc.,etc., we could achieve a possible 190-195 b.h.p. from the engine, although,might I say, this figure has yet to berealized. Straight away we find we aredown on the power of the F.V.A. en-gine by 25 - 30 b.h.p. To a certainextent this deficiency can be offset.By an intensive lightening programmeinvolving the use of as manyfibreglass components as possible,the weight of a Vitesse can be re-duced to just under 15 cwt. so a littleof the lost power is made up for byhaving slightly less weight. Even so,our power to weight ratio is still downby 8-1/2%. There is a possibility thatwe can offset some of the disadvan-tages of this lower power/ weight ra-tio in the suspension department.

Unlike the F.V.A. Escort, the Vitessehas an independent rear suspension.This means we have less unsprungweight to contend with which theoreti-cally should result in better road hold-ing. Against this must be added thefact that the Vitesse is one of the fewcars which still utilizes a chassis whichin all probability is not as stiff as a unitconstruction body. The result of thisis that our carefully planned suspen-sion geometry may not follow the ex-act motion it was intended to. In point-ing this out I may be leading you tobelieve that even a fully developedsuspension will be inadequate for ourpurposes. This is not the case. TheTriumph rear end will give better re-sults than a conventional solid axlebut its superior

9

10

ity might not be quite as much as onewould expect.

Having made our comparison, itcan be seen that a really competitiveTriumph is not by any stretch of theimagination impossible. It may be abold assumption, but I would predictthat we are likely to see far more ac-tion in the next few years providingno great restraint is placed on the situ-ation.

In an effort to encourage Triumphowners or would-be Triumph ownerson to greater deeds in the field of com-petitive motoring, this book has beenprepared. In the main it will give triedand proved methods of obtainingmore performance. Here and there

ideas will be put forward which arealthough untried based on sound en-gineering practice.

These ideas will show a gain inpower but the amount gained can onlybe estimated. It has also been recog-nized that not everyone is bent on pro-ducing an all-out racer, so all modsdescribed will start from square oneand progress from there. For thoseof you who are not fully acquaintedwith your car, it is a good idea to pur-chase a workshop manual for the rel-evant machine. This book is not in-tended in any way to replace anowner’s manual but to supplement itfor the purposes of achieving a higherperformance.

11

SINCE the conditions of the bottomend of an engine can have a majorinfluence on power output, we shalldiscuss, thoroughly and in detail, howto go about building up the bottom endwith a view to extracting the maximumhorsepower for a given state of tune.

If the car you are working on is sec-ond-hand and has seen a normalmileage, then it is more than likelybelow par. It is also noteworthy, sincewe are on the subject, that 99 out of100 new engines can benefit as faras power is concerned by a carefulprecision rebuild. In this chapter weshall deal with the 1600, 2000, and2500 c.c. six-cylinder engines. The2litre and 2.2-litre engines will be dealtwith in the following chapter.

Degreasing

The first move is to take the engineout of the car and degrease it with asuitable cleaning agent. Then, givingyourself plenty of working space, stripthe engine down and where neces-sary, number components for replace-

ment in their original position. Checkthe cylinder bores for wear. The stan-dard sizes of the bores are as follows:

1600STD 2,6276-2.6287

20002.9405-2.9416

25002.9405-2.9416

In the standard bores the pistonsare graded in three different sizes andthe bore clearance on a new enginewill be between 3.5 thou and 4.2 thou(0.00350.0042). If wear has takenplace we must determine the amountof clearance which exists before wecan say whether or not a re-bore isrequired. These engines were fittedfrom the factory with either solid skirtor split skirt pistons. Ideally the boreclearances which we should aim forare 0.005" for the 1600 motor, whensolid skirt pistons are used, or 0.0055"when split skirt pistons are used. Ifthe engine is to be used solely forcompetition work, the bore clearanceshould be 0.0055" with solid skirt pis-tons. The use of split skirt pistons

chapter IOVERHAULING THE SIX CYLINDER ENGINE

12

checked for size. If they are too tightwe are likely to encounter stickingrings and if too loose, the rate of ringwear will increase and cause gasblow-by.

The ring gap can best be measuredby using a ring and a feeler gauge.As new, the normal ring clearancevaries for the compression rings from0.0019" to 0.0035". For our purposesthe ideal clearance is 0.002". It maybe difficult to achieve this figure with-out sorting through a number of pis-tons which can make life a little diffi-cult. Whatever the case may be, thering gap should not be allowed to ex-ceed 0.0035' which is the top limit ofclearance as new from the factory.The oil control ring should be a slightlycloser fit in its slot. The normal toler-ances for the clearance are 0.0007'

in a competition motor is not to be rec-ommended. Also one should avoidthe use of pistons with a ring belowthe gudgeon pin as this creates extrabore drag On the 2000 and 2500 c.c.engines we should have a piston tobore clearance of 0.0055" for fast roadwork and 0.006" for competition pur-poses. Here again we must avoid theuse of split skirt pistons or pistonswhich have an extra oil control ringbelow the gudgeon pin.

When determining the bore clear-ance which exists, be sure to mea-sure the piston diameter at rightangles to the gudgeon pin and at apoint as shown in Fig. 1. The reasonfor this is that the pistons are both ta-pered and oval. Should the bore clear-ance prove excessive then ideally arebore is called for. The best pistonsto use are those supplied by Tri-

Grade F G H1600 2.6264/2.6267 2.0968/2.6271 2.6272/2.62752000 2.9384/2.9388 2.9388/2.9392 2.9392/2.93962500 2.9380/2.9384 2.9384/2.9388 2.9388/2.9392

umphs. In the event of the bores hav-ing less clearance than required,some honing should be done. Thebores, whether rebored or not, mustbe honed to a 20 micro inch finish witha cross hatch patter at 450 Do not at-tempt to use any other type of finishother than this or it will cost you a dropin power in the long run.

Piston fits

Having prepared the bores oneshould next ascertain whether the pis-tons are fit for re-use. The diameterof the skirt will have already beenchecked in connection with borepreparation. For reference purposesthe following chart gives the gradedsizes of the pistons.

The ring slot widths should be

to 0.0027'. For our purposes weshould try to achieve a clearance of0.0015'.

Before fitting the rings to the pis-tons, they should be gapped. The1600 motor should have the gaps onall the rings set at 0.010". The cor-ners of the gap when viewed fromabove should have a 0.005" - 0.010"radius stoned on to them. The gap onthe 2000 and 2500 c.c. engines is bestset at 0.012' and again a radius of 5to 10 thou. should be stoned on to thecorners of the gap.

Finally, before fitting any rings,check them for flatness on a surfaceplate or a piece of plate glass. If thereis any detectable sign of warpage re-ject them. Check the fit of the gud-geon pin in its bore. If there is theslightest evidence of sloppiness

13

then either piston, gudgeon pin orboth must be replaced.

Con-rods

We will now focus our atten-tion on the con rods as these itemscan cause a profound drop in powerif they are not true. Since con rodsare amongst the most heavilystressed items in an engine, it is awise move, before using them, tohave them crack tested. Once theyhave passed any crack detectiontests, checks for truth should be car-ried out. First off measure the bore ofthe big end (without shells). This mustbe 2.0210'-2.0215’dia. for all engines.

The little end should be asnug slide fit on the gudgeon pin, i.e.the gudgeon pin will not quite fall outunder its own weight but can easilybe pushed out with thumb pressure.The rods can now be checked forstraightness. For our purposes the

maximum error in bend whenchecked across the gudgeon pin mustnot exceed 0.0005" and the maximumallowable twist should not be morethan 0. 001 “.

To make things absolutelyclear as to what we are checking, re-fer to Fig. 2. This shows the effect ofbend and twist greatly exaggerated forthe sake of clarity. If you do not botherto check the rods, then you will surelypay for it in increased oil consump-tion and reduced power output. Thoseof you who have a lathe and a dialindicator, can check the rods your-selves. For those who have not, mostmotor machine shops possess suit-able equipment to do the job. Shouldany of the rods prove to be out bymore than 0.007", then it is a goodidea to replace them with new rods.Even if you have had to resort to newrods, do not accept the fact that be-cause they are new

14

they must be right. Check them to besure they are right.

Big end bolts can be a critical areaon the rod assembly. Repeated torqu-ing up and prolonged use causesthem to stretch a small amount. Toavoid any unnecessary failures in thisarea, the bolts should only be usedonce. It may seem unduly expensiveto replace these bolts just becausethey have been used once, but if arod lets go, then the chances are itwrites off a whole engine.

The cam

Moving on to the cam, we find thatthe standard journal clearance variesbetween 4.6 thou. (0.0046) and 2.6thou. (0.0026). Ideally we want thisclearance at about 3 thou. (0.003).Some blocks have cam bearings forthe journals to run in and some donot. If you have one with bearings,then it is a lot easier to achieve the 3thou. clearance since new bearingsare usually on the tight side. If youhave a block without bearings, theseare usually the earlier ones, then bear-ings should be fitted. If you intendusing a hot cam, then it is even morestrongly recommended that you usecam bearings.

When installed, the cam must ro-tate freely. To put a figure on it, thecam should, when lubricated with thinoil, rotate when a torque of 1 oz. ft. isapplied. If you have your clearanceat 3 thou., and the cam seems stiff,the usual fault is a bent camshaft.Needless to say, it is not the donething to use a bent camshaft. Inspectthe cam lobes for wear. If there is anysign of deterioration, then replace thecam. Early 1600 Vitesses had camfollowers having a diameter of 0.687".These were later replaced by camfollowers of 0.800' dia. which is the

same size as fitted to the 2000 and2500 engines. The small diametercam followers can be a weak point inthe engine, especially if a hotter camis to be fitted. On engines with thesmall cam followers, it is a straight-forward job to machine out the fol-lower bores to accept the larger camfollowers.

The 1600 and 2000 engines use asingle row timing chain to drive thecam. The 2500 c.c. engine uses aduplex timing chain. For the sake ofextra reliability on a tuned engine, onecan use the duplex set up of the largeengine on either of the smaller en-gines.

Crankshaft

The crankshaft of an engine is justabout the hardest working compo-nent. Bearing this in mind, it is onlyfair that we give the crank every op-portunity to show good service. If thecrank has already seen a reasonableperiod of use, it will not take too kindlyto all the increased loads broughtabout by tuning and the use of extrarevs. If we hope to achieve a reason-able life from the bottom end of theengine, then we must give it a goodchance to start with. This is not to saythat the bottom end is in any way un-reliable, but if we tune the engine weare expecting the crank to withstandloads in excess of those it was origi-nally designed to cater for. Thismeans that we can accept no halfmeasures. The crank must be in A.1condition before we can consider itsuse.

The 1600 and early 2000 enginesup to about 1966 use virtually thesame cranks. The main bearing sizeis 2.0005"/2.001 “ dia. If the main jour-nals are more than 0.0003' below thebottom limit, or they show

15

16

The above sizes for the crank doesmake the assumption that the bear-ing shells that are used are in themiddle of their size tolerance. Themain bearing clearance with thesecranks is between 1.2 thou. and 2thou. (0.0012 -0.0020-). We shouldattempt to get an initial clearance withnew shells of 1.5 thou. When theshells have run in and everything hassettled down, this clearance will haveopened up to about 2 thou., which isjust where we want it. The big endsshould also be treated in a like man-ner as far as clearances are con-cerned.

Assuming the block has been fullyprepared, we can now install the crankand in doing so make certain func-tional checks. Fit the bearing shellsinto the main bearing caps and block,place the crank in situ and oil the mainjournals. Fit the caps and torque downthe bolts to 50-55 lb. ft. for 1600 and55-60 lb. ft. for the 2000 and 2500engines. Check that the crank spinsfreely i.e. it should rotate when a

torque not exceeding 1/3 lb. ft. is ap-plied. If the torque required to turn thecrank is appreciably above this figure,then you have either a tight bearingor bearings, or a distorted crankshaft.You can determine whether the cul-prit is a tight bearing or not by loosen-ing off each bearing cap in turn to seeif this frees the crank. In nine casesout of ten, tight bearings can be curedby swopping the shells from onehousing to another. In the odd onecase out of ten, you will have to getsome more shells. If you want to num-ber your bearing clearance exactly,then I would suggest the use ofplastigauge clearance gauges. Thesegauges allow quite an accurate mea-surement of the clearances existingto be obtained. If each individual bear-ing clearance is correct, yet the crankis still stiff, then this points towards adistorted crank. There is also a verysmall chance that the block could bedistorted which would also cause thecrank to be stiff. If the crank you areusing has been reground or is a new

any signs of ovality or taper, then thecrank should be reground. The crankpin diameter standard is 1.8750"/1.8755". Here again we should treatany discrepancy from the true size byregrinding

The cranks from the 2500 and thelater 2000 c.c. engines differ inas-much as that they are endowed withmuch larger main bearing journals.These are some 3/16" bigger in di-ameter than the lesser or earlier en-gines. The mains journals should fallbetween 2.3110' and 2.3115" diam-

Big end standard Mains standard1600 & 2000 (up to 1966) 1.8753' 2.0008"2500 & 2000 (after 1966) 1.8753" 2.3113'

Big ends 0.010' O/S Mains 0.010 “ O/S1600 & 2000 1.8653' 1.9908'2500 1.8653' 2.3013'

eter, and should the limiting tenth of athou. below bottom limit exist, then aregrind must be done. If you are se-lecting a new crank or having onereground, then you should go forcrank pin and journal sizes about0.0002" below top limit. When usinga reground crank, we should avoidgoing below 0.010' undersize if anyreasonable degree of tuning is envis-aged. The following list gives the idealsizes of crankpin and journals to usewith a standard crank and a 0.010"regrind.

17

18

one, the chances of the crank beingout of true are very small but never-theless should not be ignored. Themost likely case of a distorted crankwill arise with those which have seenuse but not enough to cause them towear outside of the tolerances re-quired. This means a regrind will berequired to rectify the inaccuracy.

Block distortion

Lastly we can on very rare occa-sions, get block distortion. Whenblocks are cast they have stressesset up in them due to differing ratesof cooling when casting. Over a pe-riod this causes the casting to movei.e. small changes of shape occur.This means that if the block was ma-chined a short period after it had beencast, then over a period of a fewmonths it can distort itself by a num-ber of thou. whilst the castingstresses settle down. There are twoways to overcome the effects of in-ternal stresses in castings. The firstmethod is to leave the castings toage, then rough machine them andthen give them a further ageing pe-riod. After this period, which can beas much as a number of months, thefinal machining is carried out. Thesecond method is to heat the blocks

in a furnace after they have been castto allow the stresses to quickly settleout. Just once in a while it is possibleto find you are the proud owner of ablock which has not been properlystress relieved. Unfortunately thisdoes not show up immediately butusually makes itself felt some twelvemonths after, or the first time the en-gine is completely stripped. In theunlikely event that you have a dis-torted block, the only remedy is to re-place it.

We have now carefully prepared allthe major components connectedwith the bottom end. Things like oilseals, timing chains, etc. should bereplaced as a matter of course. Thecrank, rods, pistons, flywheel, clutchand crank pulley should now be bal-anced. This will not only make an al-ready smooth engine smoother, butgive that little extra reliability neededfor high performance motoring.

Valve guides

The only other points connectedwith the mechanical well being of theengine are associated with the cylin-der head. The wear on valve stemsand guides must be checked. Thevalve stem sizes for the three enginesare as follows:

Inlet Exhaust2000 & 2500 0.3107'-0.3112' dia. 0.3100 “-0.3105' dia.1600 0.3100'-0. 3110 dia. 0.3090"-0.3080" dia.

The bore of the inlet guides arecommon to all engines, this being0.312"-0.313" dia. As you can see theclearance on the larger two enginescan, on the inlet, vary between 0.0023'and 0.0008'. The clearance to achieveis between 0.001 “ and 0.0012'. Onthe exhaust side the clearance canvary between 0.003” and 0.0015'. Forour purposes 0.002" clearance isneeded. On the 1600 engine the stan-dard clearance on the inlet valve can

be between 0.001' and 0.003". Herewe need 1 to 1.2 thou. clearance(.001" 0.0012"). The standard clear-ance on the exhaust valve on 1600engines is by normal standards large,this being between 3 and 5 thou.(0.003"-0.005"). One should endeav-our, where possible, to select com-ponents which will set this clearanceat the lower limit of 0.003".

You may wonder why the valve to

19

valve guide clearance has been goneinto in such detail. The main reasonis that the motion of the valve mustbe controlled in such a manner as toallow the valve to move in a straightline only. The more clearance one hasthe less likelihood there is of achiev-ing the required motion. Excess clear-ance will cause an increase in oil con-sumption, a small drop in power andan increased valve seat wear rate.The last point is especially relevantwhen we consider the use of radiusvalve seats which will be thoroughlydiscussed later in the book.

Before winding up our dimen-sional check of various engine com-ponents, we should check out therockers and rocker shafts for wear.Normal clearance is between 1.8thou. and 3.3 thou. (0.0018" - 0.0033')If the clearance is more than 0.005'above the upper limit, steps shouldbe taken to remedy it. Rockers which

are too loose can set up a mode ofvibration which does nothing to en-hance valve timing at high revs., es-pecially if the cam is of a hotter vari-ety.

Assembly

We should now come to thetime when we are able to put the en-gine together. Assemble the crank,rods and pistons into the block usingengine oil on bearing and rubbingsurfaces. Having assembled the en-gine, we now come to the test whichwill verify your dimensional checking.Rotate the crank assembly about fiftytimes. Then using a torque wrench,establish the torque required to turnthe engine over. The absolute maxi-mum torque required to turn the en-gines over are 20 lb. ft. for the 2500,16 lb. ft. for the 2000, and 12 1/2 lb.ft. for the

20

1600. If the build up has been donecarefully, these torque figures can beas much as 30% lower. If the figure issignificantly higher, then something isamiss, so you should go through whatyou have done to locate the cause ofstiffness. Excess internal friction in anengine is a sure way to lose power. 5lb. ft. of frictional torque over andabove our minimum will cost us 6.7b.h.p. at 7000 revs. As you can see,the moral is to build up an enginewhich is as free as possible whilst stillfailing in with our component dimen-sional limits.

With the exception of a couple ofpoints, the engine assembly fromhere is straightforward. The couple ofpoints which we must bear in mindare connected with the accuracy andconsistency of our ignition timing. Thedistributor is driven in a conventionalmanner by a skew gear coming offthe camshaft. As with any gear train,backlash is necessary but on theseparticular engines we have a measureof control over the amount of back-lash present. The total backlash which

can be present at the distributor driveshaft is not only the backlash of theskew gears but also an amountcaused by the end float of the cam-shaft. Our camshaft end float is con-trolled by a thrust plate at the timingchain end of the engine. The normalcam end float is between 0.004' and0.008". By selecting a suitable platewe must get the endfloat down to0.004'. We can, if we are going to beultra fussy about it, reduce this to0.003' but we must definitely not gounder this figure.

The other area which must beclosely looked at is the end float ofthe distributor drive shaft itself. Thestandard clearance figures range be-tween 3 and 7 thou. and the figurewe want is 3 thou. on the nail. Fig. 3shows the precise method to adoptfor determining this clearance andsetting it to the required figure. As-suming we have a perfect distributor,any erratic timing caused by excessbacklash can cost around 2-3 b.h.p.,so play close attention to these endfloat settings.

21

WITH any tuned or hard pressed en-gine, the lubrication system must bein perfect order or better still, upratedto cope with more stringent condi-tions.

The standard oil pump is capableof coping with the extra demandsplaced upon it by a modified engine ifit is in perfect order. However, to en-sure a good engine life, a little timeand trouble spent on the standardpump will not go amiss. The work in-volved on the pump includes a thor-ough check on clearance existing andrectifying these where necessary. Fig.4 shows an exploded view of thepump assembly just so that we knowwhat bits we are talking about. Themain object of the exercise is to buildup a pump assembly having the mini-mum clearances between the bodyand the outer rotor and between theouter rotor and inner rotor, A normalvalue for these clearances is around0.007'. By selecting components, wecan quite easily get this figure downto 0.004' and if a great enough num-ber of components are available thiscan be reduced further still. Theseclearance values can easily be

chapter 2IMPROVING THE LUBRICATION

checked with feeler gauges as shownin Fig. 5 and 6. The only clearancethat we can readily make adjustmentsto is the end float between the innerand outer rotor and the end plate. Bymachining a small amount off thebody we can set the end float to 0.001“thus reducing any leakage at this pointto a minimum. Fig. 7 shows how theend float clearance can be measuredso as to enable the correct amount ofmetal to be removed.

When machining the pump body,be very careful as there is very rarelymore than 0.003' to come off. Whilstmachining the body, you must alsomake sure that the inner and outerrotor are of identical length or you willhave a different end float for eachcomponent. Once all the pump com-ponents have been selected or ad-justed as necessary, the pump canbe assembled. Using very light oil toprovide a little lubrication, check thatthe pump rotates smoothly and freely.Having gone to all this trouble to pre-pare the pump, we can expect it tobe about 7-10% better than the aver-age pump. This may not sound like a

22

23

24

fantastic gain for all the time andtrouble resorted to, but we must re-member it is always the last straw thatbreaks the camel’s back. The in-crease is sufficient to give us that ex-tra margin of safety between retain-ing or losing the vital oil film betweenthe highly stressed components.

Pressure release valve

Still on the subject of lubrication,suitable adjustments should be madeto raise the pressure at which thepressure release valve comes intooperation. This can be achieved quite

simply by increasing the spring pres-sure which is exerted on the pressurerelease valve. A spacer made up asshown in Fig. 8 and fitted under theface of the release valve spring re-taining bolt will do the trick. Thespacer will cause a raise of 10-12 lbs.per square inch of oil pressure beforethe pressure release valve comes intooperation. It will be found unneces-sary to so such a mod to the springpressure unless the engine spends agreat deal of its time in the upper revo-lution range as would an engine usedin competition.

25

THE 2 and 2.2 litre four cylinderTriumph engines are well noted fortheir long life and ruggedness. If theengine is carefully assembled, theneven in a relatively highly tuned state,reliability does not suffer to any no-ticeable degree providing one paysstrict attention to the rev limit. Weshould apply the same thorough nessand attention to detail as was outlinedin Chapter 1 on the six cylinder en-gines. To avoid unnecessary repeti-tion of the whys and wherefores, thetolerances that we should work to willjust be quoted with only limited expla-nation as to why.

Assuming the engine has been re-moved from the car and has beencompletely stripped, we should be ina position to carry out our dimensionalchecking. As good a point as any tostart with is the block. A close look atthe block will reveal that, unlike mostengines which have pistons runningdirectly in the block casting, the Tri-umph engine has removable wet lin-ers. The definition of a wet liner is onethat is directly in contact with the wa-ter, as opposed to one that is in con-tact solely with the cast iron of the

block. Anyway, to get back to thepoint, we should check the bore forwear. Since this particular engine hasbeen out of production for some time,I should doubt if any engines whichare still on standard size pistons arenot in need of a rebore. The standardsize of bores for the 2-litre engine andthe standard piston to bore clear-ances are as follows:

Standard Standard bore clearance

Std. 3.2677" 0.0042'+ .020” 3.2877” “+ .030” 3.2977” “+ .040” 3.3077” “+ .060” 3.3277” “

For fast road work the bore clear-ance should be 0.005' and for racing0.006'. When determining the piston/bore clearance, the piston should bemeasured level with the gudgeon pinbut at 901 to it. If the piston to boreclearance exceeds 0.008", then arebore will be required if we are toachieve optimum power. With the 2.2litre engine the

chapter 3BOTTOM END PREPARATION

26

standard bore and rebore sizes willbe:-

Standard Standardbore clearance

Std. 3.3854” 0.0043”+ .020" 3.4054” “+ .030" 3.4154” “+ .040" 3.4254" “+ .060" 3.4454" “

For road work we want a 5.3 thou.clearance, and for racing a 6.4 thou.clearance. The bore sizes alreadyquoted are those which give a stan-dard clearance. Since it is easier toobtain extra clearance by making thebores slightly larger, than it is to re-duce the sizes of the pistons theabove bore sizes will want enlargingon. To obtain the correct clearanceusing new pistons, the following chartshould be adhered to :

2-litre engine Road RacingStd. 3.2685” 3.2695”+ .020" 3.2885” 3.2895”+ .030 “ 3.2985” 3.2995”+ .040" 3.3085” 3.3095”+ .060 “ 3.3285” 3.3295”

2.2-litre engineStd. 3.3864” 3.3875”+ .020" 3.4064” 3.4075”+ .030" 3.4164” 3.4175"+ .040“ 3.4264” 3.4275”+ .060" 3.4464" 3.4475”

The bores should be finished byhoning to 15-20 micro inch finish witha cross hatch pattern of 45".

As has been stated before, thisparticular engine has removable lin-ers which leads us to some interest-ing possibilities as far as increasingits capacity is concerned. The linersfrom the 2.2 litre engine can be fittedto the 2litre engine, thus bringing it upto the same size as its bigger brother.Also there is a 9.25/1 piston made byHepolite which will give a further slightincrease in capacity. This piston has

a standard size of 3.4252" (87 m/m)and is available at rebore sizes of+030” and +040”. The 2.2 litre linerscan be bored to take this piston butthe 2-litre ones cannot. If we use thispiston (Hepolite part number 13958)in its +040” form we will bring the ca-pacity up to 2239 c.c. from the origi-nal 2138 c.c. If this piston is used inits standard 87 m/m form rather thanin oversize form, the capacity is 2187c.c. For the purposes of building up ahigh performance road or race enginethe use of this piston is to be recom-mended. Its advantages lie in the factthat it is quite light in weight, has noring below the gudgeon pin and is ofthe solid skirt variety. The boring sizesfor this piston are:

Road RacingStd. 3.4262" 3.4273”+.030" 3.4562" 3.4573”+.040" 3.4662" 3.4673"

If the Hepolite piston just mentionedis not used, then it is advisable to usepistons supplied by Triumphs. Thereare some pistons on the market whichhave an extra oil ring below the gud-geon pin. The use of these is to beavoided as are pistons having splitskirts.

Liners

If by some chance, your engine hasalready been bored to its maximumsize and is yet again in need of arebore, then it will be found neces-sary to fit new liners. This in itself is asimple enough job, but one whichmust be done properly if we are toavoid any possible leakage fromjoints.

First off, one should remove the oldliners. It is definitely not advisable totry bashing out the liners solely withthe aid of a hammer. To do the jobproperly without incurring any nastyside effects, one

27

should make up a special tool to dis-tribute the hammer blow evenly overthe end of the liner. The dimensionsfor such a tool are shown in Fig. 9.Place the block, head face down, onsome blocks of wood. Place the linerremoving tool into the bore of thelinerthe crank end of the liner. Placea suitable stout punch i.e. 1 ‘ dia. steelbar on top of the removing tool andhit the punch with a heavy hammer.In most cases the liner will come outwithout undue trouble. Occasionallyan obstinate liner is encountered, butthe application of a little penetratingoil will ease the situation. Having re-moved all the liners, thoroughly cleanthe area on which the bottom jointinggasket seats see Fig. 10. This areamust be perfectly free from foreignmatter which may prevent a perfectseal being formed. Smear the newliner sealing gaskets with a non-set-

ting jointing compound. Fit the newliners in position and as soon as pos-sible afterwards, fit the head togetherwith an old head gasket and torquethe assembly down to about 6070 lb.ft. Fitting the head effectively pullsdown the liners, seating them firmlyonto the gaskets. The head can nowbe removed so that we can check theliner protrusion above the block face.Place a straight edge across the topof each liner, and using a feelergauge, check the gap between thestraight edge and the block face seeFig. 11. This clearance should be be-tween 0.002"0.005'. In all probabilitythe protrusion of each liner will varybetween these limits. If the protrud-ing height of each liner is the same,then you have just been lucky. In thegreater likelihood that each linerheight varies one to another, a littlemachining is called

28

for. The top faces of the liners shouldbe skimmed to bring them all to thesame height above the block face.This height, however, must still remainwith the 0.002" - 0.005" tolerance. Ifyou should find that the protrusionheight is less than 0.002", then theliners will have to be removed and afew thou. taken off the top of the block.Having done this, refit the liners asdescribed previously, and machinethe tops of the liners to bring them allto a common height, within the speci-fied tolerance.

Rings

Having, we hope, successfully pre-pared the bores, we can turn our at-tention to the piston rings. As usual,for high performance engines, weshould check the rings for flatnessand for ring to groove clearance. Thefactory limit for ring to groove clear-

ance is 0.001 “-0.003'” We definitelyshould not allow the clearance to ex-ceed these figures and ideally if a se-lection of pistons is available, thisclearance should be at 0.0015'. Thering gaps for all rings should be set to0.012'-0.015' and the corners of thegap stoned off to a 0.005"0.010" ra-dius.

The tappets or cam followers mustbe a free fit in their bores but on theother hand should not be sloppy. Themaximum tappet to bore clearancewe can tolerate is 0.0016'. Since mostof the wear seems to occur on thecam followers rather than the bore,any wear problems can usually beovercome by fitting now cam follow-ers. If a new standard cam or a highperformance cam is to be fitted, thenew cam followers are essential nomatter what condition the originalones are in. If this Is not done youhave a 90% chance

29

of having a cam life of less than a fewthousand miles. Whilst we are on thesubject of cams, the camshaft must,when fitted into the block, rotate freelyand smoothly. A bearing clearance of0.002' being ideal and 0.0037" clear-ance is the maximum allowable clear-ance for all the bearings bar the frontone. The clearance on the front bear-ing is best around 0.003" and themaximum that is permissible is0.005".

To avoid undue power loss, the rodsmust be true within fine limits. Themaximum bend when checked overthe length of the gudgeon pin shouldnot exceed half a thou. (0.0005") andtwist should not be greater than 0.001“. Chapter 10 will clarify the conditionswe are ideally seeking to minimise.

Big ends MainsStd. 2.0861 “-2.0866 “ 2.4790”-2.4795"0.010, 2.0761 “-2.0766 “ 2.4690”-2.4695"0.020' 2.0661 “-2.0666” 2.4590"-2.4595"

The little end of the rod must be asnug fit on the gudgeon pin. This usu-ally means a clearance of 0.0002"/0.0004". Although these engines arenot prone to rod break ages, it is agood idea to play safe and have themcrack tested and as another precau-tionary measure, fit new big end boltseach time the big ends dismantled.

As has been said before, we aredealing with an engine which hasbeen out of production for some time.It is therefore reasonable to assumethat in most cases the majority of theuseful crankshaft life has been used.This will mean that nine times our often a crank regrind is called for. Thelimits of crank journal sizes are shownbelow at standard size and 0.010' and0.020" undersize.

30

For a road going engine, a crankregrind to -0.040" is passable. On theother hand, if the engine is to be usedfor serious competition, the 0.020"regrind should be regarded as maxi-mum. It is always difficult to knowwhere to draw the line as far as crankregrinding goes. Each step of 0.010"does not reduce the crank strengthby a vast margin, but going from stan-dard to 0.060" does. Since the crankin standard form is only safe to 6500continuous or 7000 instantaneous, wemust conserve all the crank strengthpossible. These engines will seem-ingly last for ever at 6000 r.p.m. butat 7000 the life can be measured inminutes.

Assembly

We should now be in a position toassemble the bottom half of the en-gine. The first move is to fit the crankand check for stiffness, The methods

of pinpointing the cause of stiffnessand its remedies were outlined inChapter 1 concerning the six cylinderengines. The fitting of pistons and conrods follows normal procedure. Wecan, at this stage, assess the turningtorque of the crank/rods and pistonassembly. If all is well then the assem-bly should rotate when a torque notexceeding 24 lb. ft. for a road engineand 20lb. ft. for a race engine is ap-plied. If the torque figure is signifi-cantly higher than this, then some-thing is amiss, in which case, if youare wise, you will strip the engine tofind out why. The difference betweenthe turning torque for a road engineand a race engine, arises from thedifferent bore clearances. Once theengine has run in, this torque figurewill drop and the difference betweena road and race engine will drop from4 lb. ft. to about 2.5-3 lb. ft. This dif-ference may sound like a trivialamount to worry

31

32

about, but it is worth about 4 b.h.p.and 6500 revs. and with a race en-gine every little bit counts.

As with the six cylinder engines, wemust pay close attention to the cam-shaft end float, and the end float ofthe distributor drive gear. The frontcam bearing is removable and hason it a flange which controls the depthto which it can go into the block seeFig. 12. The normal cam end float is3 to 7.5 thou. (0.003" to 0.0075").Since we want the most accurate ig-nition timing possible and since camend float effects the ignition timing,we must reduce the cam end float toa minimum. The minimum is at 2 1/2. to 3 thou. (0.0025"-0.003"). In vir-tually every case the existing end floatwill be more than we want. To reducethe end float down to the figure weneed, some machining will be calledfor on the abutment face of the flange

on the front cam bearing. This facewill need skimming on a lathe to givethe end float required.

This leaves us with only the distribu-tor drive gear end float to contendwith. On a standard engine this canvary between 0.003" and 0.007”. Forour purposes, the 0.003' setting isrequired. The technique for settingthis is virtually the same as for the sixcylinder engines and is shown in Fig.of Chapter 11. Building up the remain-der of the bottom half of the engine isa straightforward procedure. All gas-kets and oil seals should be replacedduring the rebuild. The timing chainshould also be renewed. If all thestated tolerances have been adheredto, and a great deal of intelligent careapplied, the end result will be wellworthwhile as far as power and reli-ability are concerned.

33

THE 1600 Vitesse Mk. 1, 2-litreVitesse Mk_ 1, G.T.6 and early 2000saloons use a head which is basicallycommon. The Mk. 11 Vitesse andG.T.6, TR5, TR6, and the 2.5 P.I. sa-loon use a different head. The heads,as far as fitting is concerned, are in-terchangeable between the early andlate models. The major differencebetween the two basic types of headlies in the chamber design and themanifold joint face. It any headchange from early to late models iscontemplated, then the manifoldsmust be changed to suit. The laterheads also sport a larger inlet valvewhich assists breathing. The largervalve, together with the redesignedchambers gives an increase in powerof about 7%. Since cylinder heads areso expensive, one should only con-sider changing the head if the ultimatein power is required because the earlyheads can be modified to give resultsvery nearly as good. In this chapterwe will deal specifically with the earlytype of head. It is quite simple to de-termine which type of head you haveby comparing your own head with thehead drawing in this book. The early

heads have the manifold joint faceterminating about 1 “ from the edgeof the casting when viewed end on.The later heads, however, have themanifold joint face terminating flushwith the edge of the head casting.

We will start off with a Stage 1 typeof head for the 1600 and Mk. 1, 2-litre Vitesses, Triumph 2000, earlytype, and the Mk. 1 G.T.6.

Removing guides

Strip the head of all parts so thatyou are. left with the bare head cast-ing. I personally do not like the use ofa hammer to remove valve guides. Ifyou are using a heavy hammer to re-move the guides you only have tomiss the guide removing drift or catchit at a slight angle to do the head aninjury. By far the best way to removeguides is by using a press. Of course,if you find that none of your local mo-tor machinists or garages have one,then the only alternative left to you isthe large hammer. Either way, pressor hammer, a guide removing drift willbe required, the relevant dimensionsof which are given in Fig. 13.

chapter 4

MODIFYING THE EARLY 6 CYLINDER HEAD

34

Thoroughly clean the head faceusing emery cloth as required, so asto achieve a surface suitable for mark-ing on. Apply marking blue to the headface. Marking blue, by the way, isavailable at any hardware store deal-ing in engineers’ tools. While you areat it, you will also need a tin of engi-neers’ blue. For those of you not fa-miliar with either of these compounds,marking blue is a marking agentwhich dries very quickly, in fact, in onlya number of seconds. Engineers’ blueon the other hand is a marking agentwhich virtually never dries out and isused to detect and show up points ofcontact, i.e. high spots between mat-ing surfaces. We find the engineers’blue virtually indispensable later whenlapping in valves.

At this point we will need tomake up a template to accuratelymark out our new chamber shape. Inthis particular instance, the best bet

is to make one from perspex of 1/16”thickness. The drawing of the cham-ber Fig. 15 is to scale so the cham-ber shape can be traced on to theperspex from the drawing. When trac-ing this shape, do so as accuratelyas possible, as there is very little roomfor error. A badly traced template anda little erroneous grinding later cancause a scrapped head. Trace outboth the original shape and the newshape on the perspex and if possible,trace out the shape on both sides ofthe perspex to reduce to a minimumany effects of parallax due to the thick-ness of the material. Inspection of Fig.15 will show that the chamber is onlymodified over part of its perimeter. Ifwe now cut the perspex only alongthe reprofiled part of the chambershape Fig. 14, then we can use therest of the chamber outline, whichremains unchanged, to line up ourtemplate. The chambers in

35

36

37

the head are “handed.” To mark outan opposite handed chamber wemerely turn the template over onto itsother face. Once you have conscien-tiously made your template, the headmarking out procedure can begin.

To do so you will need a very sharpscriber, and also one which has a longtapered point with, say, an includedangle of about 300, not a short stubbypoint. The only reason for this is thata short stubby point will inevitably pro-duce a line which does not coincidewith the edge of the template but is ashort distance out from it. As I havementioned previously, we have virtu-ally no room for error on the ,cham-ber shape, or we shall infringe, if thatis the word, into the domain of thegasket.

We can at last start grinding, butfirstly some more words of caution. Ifyou are the proud possessor of asteady hand you will find that on thishead you have enough room to beable to avoid serious contact betweenthe grinding wheel and valve seat. Ifthis is the first time you have at-tempted any serious head work or youare not at all sure that you have asteady enough hand, then it is best totake a few precautionary measures.First off, take a couple of scrap valves,one inlet, one exhaust, and machinethem across the head face sufficientlysuch that when they are fitted in posi-tion the valve head face is flush withthe chamber roof. Next, tap the valveguides a short distance into the head,just sufficiently to locate them. By in-serting the valves into the chamberwe are working on, we have effectivelycovered the seats and protected themfrom accidental damage.

If you look closely at Fig. 15 show-ing the chamber modifications, youwill see that although the chamber

outline over its greater part remainsunaltered, the walls of the chambersrequire fairly extensive work to bedone on them. Basically what we aretrying to achieve is a chamber wallhaving no sudden changes of form orany corners formed between angledand vertical sections of the chamber.The area of the chamber wall aroundthe spark plug, should not be touchedexcept for polishing. Although a lineis used on the drawing to depict theextremities of this area, a sharp edgeshould not be formed at this line.Machining the walls of these cham-bers requires a good eye to blend thechanging curved section into thestraight walls. The crossed sectionsshould therefore be regarded as areasonable guide as to where the wallsection remains standard.

When all the grinding has beencompleted, the chambers should bepolished to give a smooth finish. It isquite unnecessary to polish until youhave a mirror finish as all the work indoing so will be completely wasted.The type of finish required is one thatis smooth to the toucha good com-parison for this would be a piece ofchina ware.

This now leaves us with the portsto tackle, and we will deal with the in-let ports first. At this stage one mustdecide whether or not radius valveseats are to be used. Let me warnyou, it is a long and tedious task do-ing radius valve seats unless you arethe proud possessor of some sophis-ticated valve seat machining gear.Doing radius valve seats by moremenial methods can take 12-15 hourswork, and sometimes longer. The endresult of such labour is 2-4 b.h.p.more, depending on the state of tuneof the engine, than conventionalseats.

38

39

40

We will assume at this point thatconventional seats are going to beused, and deal with the radius seatslater.

Take a good look at Fig. 16 whichdepicts a cross-section of the headthrough an inlet port. A fairly largerestriction is caused by the valveguide boss. It must be pointed out,however, that the drawing, by virtueof the angle the head is viewed from,does tend to exaggerate this restric-tion since it cannot easily be seenfrom this that there is a certain amountof room for airflow around the sidesof the boss. The first step then, is togrind the boss as shown in Fig. 16,then profile the rest of the port asshown to within about 1/4” of the valveseat. If you look just under the valveseat about 3/16" down the port, youwill see a step formed by the factorymachining of the valve throat and the‘as cast’ part of the port’ Whether thisis by design or not is debatable butnevertheless for our purposes it issomewhat irksome. We can, in mostcases, when forming a venturi typeport, eradicate the effects of this step.Fig 17 which shows the port in theimmediate vicinity of the valve seat,shows how the port should be ground.We should not attempt any work onthis part of the port until the valveguide has been fitted and the valveseat recut. When grinding the port donot increase its diameter at the mani-fold face end. In fact the first 3/8" ofthe port should be as near to stan-dard size as possible.

Assuming that you have ground andpolished the ports to within 1/4" of thevalve seats, we can now fit the inletvalve guides which should be modi-fied by turning as shown in Fig. 18.Having done so, get the valve seatsrecut and finish off the careful not todamage the newly cut valve seat.

Exhaust ports

We can now turn our attention tothe exhaust port. As with the inlet portthere is a substantial amount of metalto be removed from the valve guideboss. The rest of the grindingisstraightforward reprofiling to getsmooth contours, Fig. 19 shows theport shape required. With manyheads we are likely to come acrossan irksome little step just below thevalve seat. You just have to do thebest you can to blend it out. If it is morethan 1/16", do not try to blend it outcompletely as this will tend to makethe area of the exhaust port a little toolarge at this point. As with the inletport, we adopt the same procedureby leaving the last 1/4” or so underthe valve seat until the valve guide isfitted. Before fitting the guide, it shouldbe modified as shown in Fig. 20.When the guide has been fitted andthe seat recut, the port can be finishedoff, leaving a valve seat 1/16” wide.

If you decide to use radius valveseats on the inlet side, then a differ-ent approach is required. To start with,you will need to make up a specialradius valve seat cutting tool, the de-tails of which are shown in Fig. 21.The seat radius we are going to useis 0.125" and to make sure the toolbit is accurately formed to cut this ra-dius, the correct method of approachshould be used. Firstly the tool bit isbest made up from an old centre drillof 5/16" or so diameter. Using an off-hand tool grinder, rough out the gen-eral shape of the tool. Mount a pieceof 1/4” diameter mild steel bar in alathe or drill chuck and coat it with finelapping paste. Rotate the bar andpress the roughed out form of the ra-dius against the

41

42

bar. Distribute the wear on the bar bymoving the tool bit up and down thelength of the bar. Whilst accuratelyforming this radius, be sure to hold totool bit at a slight angle, approximately100, to the bar to give the tool a cut-ting clearance. Once the tool hasbeen made up, set it in the tool holderto the dimension shown in Fig. 21.Using a pillar drill set on a slow speedto avoid tool chatter, cut the seats.Now back to the -grinder and blendthe radius seat into the port as shownin Fig. 22. At this stage in the proceed-ings you will have to leave the headand turn your attention to the inletvalves. The idea here is to reshapethe valves to assist our gas flow. Itmay seem strange at first sight, buttulip valves do not always give thebest gas flow characteristics. To getbetter cylinder filling we must reducethe tulip shape to something morealong the lines of the head of a nail.Fig. 23 shows the shape we should

aim for. Except for the actual seat it-self this shape applies to both the con-ventional valve seat and the radiusvalve seat.

Lapping in the valves

Once the valves have been re-shaped, we can start the job of lap-ping them onto our radius seats. Themethod of lapping and correcting anyerrors of concentricity are as follows.Using fine grinding paste, lap thevalve into its seat for a short periodi.e. a couple of minutes. Wipe thegrinding paste from both the valve andseat and apply a thin smear of engi-neers’ blue to the valve seat. Drop thevalve back onto its seat and rotate it.If we now remove the valve, the engi-neers’ blue will show where the valveis making contact with the seat. If theseat cutting operation was really ac-curate then the seat will exhibit a com

43

44

45

46

plete circular line. In all probability theseat will be slightly out of true and thiswill be shown up by a blue line overonly part of its circumference. In sucha case the seat will have to be dressedwith the cutting tool. Using the radiuscutting tool by hand, lightly cut the partof the seat showing the blue line. Hav-ing done so, lightly relap the valve andcheck it again with the engineers’blue. Continue the lapping, cuttingand blueing until you achieve a com-plete circle on the seat, and a seatwidth of about 0.030".

The conventional 450 angle valveseats are lapped in the normal man-ner. It is a good idea to check the va-lidity of the lapping with engineers’blue to make sure the job is up toscratch.

Skirnming the head

The final machining operation is toskim the head to achieve the desiredcompression ratio. With the Triumphheads we usually have a fair marginof metal that can be taken off, therebygiving us any reasonable C.R. that wewant. For road use, a 10/1 C.R. isplenty and for racing, about 11.5 willdo the trick. It is not easy to quote theexact amount one should removefrom the head to achieve these C.R.,but the amounts will be about 0.070"and 0.085' respectively. The best wayto determine what should come off thehead is to fill the chambers with par-affin or petrol from a burette. If we fillthe chambers with fluid to the volumerequired for a particular C.R., then theamount of metal left proud of the fluid

is the amount to remove. Here are twoexamples showing the volumes re-quired for the chambers on the 1600and 2-litre engines.

C.R.= (V+C) / C where V = sweptvolume of cylinder in c.c. and C =total chamber volume in c.c.

For the 1600 engine 1600V = 1600 / 6 = 266 c.c.

Therefore C.R. = (266 + C) / C

Therefore C.R. - 1 =-266 / C

For a C. R. of 10 to 1 we have:10 - 1 = 266 / C

Therefore:C = 266 / 9 which = 29.5c.c.

There is, however, approximately4.5 c.c. in the gasket and block whenthe piston is at T.D.C., so this mustbe subtracted from our 29.5 c.c. togive us the required volume in thehead. Our head volume therefore is29.5-4.5 —25 c.c.

This volume will give us a 10 to 1C.R. on a 1600 engine. An 11.5/1 C.R.will require a head volume of 20.8. Onthe 2000 c.c. engines to get 10 to 1or 11.5/1 we will require 32.5 and 27.2respectively.

This leaves us only the assemblyof the head to do apart from any portmatching operations that may be re-quired. The methods to adopt for portmatching are examined in a laterchapter as is the choice of valvesprings for a given application.

47

FOR an even greater increase inpower, the use of oversize inlet valvesshould be contemplated. The use ofa big valve head will come into its ownwhen other components directly re-lated to engine power have seen at-tention. For this reason we will findthat the use of larger valves is a wasteof time unless the carburation andvalve timing have been improvedupon i.e. a hotter cam and better thanstandard carburation set-up. If theengine is to receive considerable at-tention in such quarters, then the useof a big valve head is to be recom-mended. It does, however, entail alittle more than just dropping in thelarger valves. As with the Stage 1head, we have the alternative of ei-ther conventional seats or radiusseats. The choice is yours, but for thehighest power the radius seats mustbe considered the first choice.

Inlet valves

When fitting a larger inlet valve boththe inlet port and the combustionchamber are modified to a slightly dif-ferent shape to those used for the

chapter 5

BIGGER VALVES FOR EARLY HEADS

Stage 1 head. This, of course, makesthe assumption that you are using avalve about 1 /10" larger in diameter.Let us assume at this point, that thevalve to be used is 1.395" diameter,which is, incidentally, the one whichis supplied by S.A.H. Accessories ofLeighton Buzzard. The procedure toadopt to modify the head will only bediscussed regarding those pointswhich differ from the Stage 1 head.

First off, we will need a perspextemplate for the big valve chambershape which can be traced directlyfrom Fig. 24. The procedure from hereon to complete the chambers is asfor the Stage 1 head in Chapter 4.

We can now turn our attention tothe inlet port. With the guides out, pro-file the inlet port to within I/.” of thevalve seat as shown in Fig. 24. Whenthe port has been finishpolished to thisstage, fit the guides which, inciden-tally, should have been previouslymodded as in Fig. 18. A tool will berequired to bore the valve throats outto take the larger valves. If we are touse 451 conventional seats, then atool bit

48

49

fitted into the tool holder as shown inFig. 21. should be used. The settingdimension (A) will be 1.030”. The toolsetting to bore the correct size for a1.395" diameter valve is shown in Fig.25. This will give us a throat diameterimmediately under the valve of 1.310"diameter. Boring out the throat alsomeans we stand a very good chanceof completely removing the small stepwhich occurs just under the valve seaton the majority of heads. When theport has been bored to a depth of 1/8"to 3/16" blend out any irregularity withthe finished part of the port. Cut thevalve seat and lap in the valves. Nowcomes a tricky bit; put a small radiuson the inner edge of the valve seatthus breaking the sharp cornerformed by the seat at the port (Fig.26). In doing so, this should reduceour seat width to about 0.030'.

Radiusing seats

For those of you who are braveenough to tackle radius seats, you willneed the tool holder and radius cut-ting tool shown in Fig. 21. For thisparticular application, the radius of thecutting tool should be 0.140" insteadof the 0.125" shown in the drawing.Our setting dimension will also be dif-ferent.

Before you remove the inlet guidesfrom the head to grind the ports, theradius seats should be roughed out.The setting dimension for roughingout the seats, dimension A in Fig. 21,will be 1.003. Once the seats havebeen roughed out, the guides can beremoved and the ports ground to therequired form as in Fig. 27 and pol-ished. New modified guides are thenfitted and the seats finished off. To doso, the radius seat cutter, dimensionA, must be reset to 1.01 3" and care-fully recut. The finishing procedure em

50

51

52

ployed on the seats is then as detailedin Chapter 4.

The grinding of the exhaust portsand the raising of the C/R remains thesame as explained previously. Withthe big valve head it will be found thata little more is required to be skimmedfrom the head than for a Stage 1 headbecause of the greater amount ofmetal removed from the chamber.The extra metal to be removed isroughly going to amount to 7-10 thou.but this figure is intended as a guideonly. The only sure way to get the C.R.to the required level is to use the bu-rette and paraffin to measure the vol-umes and determine the correct

amount to take off.The use of this large inlet valve type

of head gives a power increase ofaround 7% over the standard valvesize modified head. It also raises thepoint at which peak power occurs byabout 200-250 r.p.m. on the 2000 c.c.engines and about 300-350 on 1600engines. If used on a 1600 engine,the rest of the engine should bebrought to a fairly high state of tuneto bring it in line with the characteris-tics of the head. Even on a 2000 c.c.engine other modifications will needto be done to make full use of such ahead.

53

THIS chapter applies to the headsused on the T.R.5 and 6, the 2000saloon from 1966 onwards and theMk. 11 versions of the 2-litre Vitesseand G.T.6. Comparisons of Figs. 15and 16 with Figs. 28, 29 and 31 willshow the basic differences in theseheads. The later head is generally ofa superior design to the early one. Theports have a more gently curved con-tour to the valve than the earlier head,thus aiding gas flow. The inlet portterminates at a valve some 0.144' big-ger than its predecessor which,coupled with the better port, shows asignificant advantage in power. Thecombustion chamber in the later headis also changed for the better and toget the best from it without completelyredesigning, there is little we can doto improve matters. A glance at Fig.28 will show just how little work is re-quired on the chambers. In plan viewthe chamber shape remains un-changed. The sum total of the grind-ing required is all performed on thechamber walls. The end result of themodifications to the chambers shouldbe a chamber wall which changes

chapter 6

MODIFYING THE LATER2000cc AND 2500cc HEADS

smoothly from a vertical to an angledwall, leaving no projecting edges inthe chamber. This tidying up of thechamber shape gives us improvedcombustion efficiency but the gainsachieved are only marginal. No doubtif we compared the difference inpower gain by the slight change inprofile, the net result may only be inthe order of 1 A-2%. Since every en-gine tuner is after every little drop ofpower within a given budget, it canbe argued that although the gain issmall, the modification is justifiable.It is surely this type of attitude towardsthe preparation of a motor that makesthe true enthusiast stand out from therest of the crowd.

Porting

Anyway, back to the subject in handwhich is now the ports. These requirelittle more than polishing. Do not, un-der any circumstances, open themup, as if anything, they are slightly toolarge now. As with the earlier type ofhead, we have the presence of thesmall step just

54

55

56

under the valve seat, the completeblending out of which is a little diffi-cult. On some heads it will blend out,but on others it will not. It just dependson the casting Another point which isa little undesirable but one we can donext to nothing about, is the pocketaround the valve guide. It could betermed a negative boss in as muchas it is a boss recessed in rather thanone projecting out. The presence ofthis inset boss means that we cannotget a smoothly contoured port in thearea either side of the guide and im-mediately behind it. From our point ofview, the presence of this depressionis a little annoying, but the TriumphEngineers in their wisdom, did not putit there for nothing. Consider the factthat the guide is a press fit in the head.If one side of the hole into which theguide is fitted is substantially longerthan the other side, the forces pre-vailing from the press fit impart un-even loads from one side of the guideto the other. This means that the guideitself becomes bent. Also the machin-ing of an accurate guide location holeis nearly impossible by productionmethods if it breaks through on anuneven surface. That explains whythe depression is there but providesabsolutely no remedy for it. On occa-sions attempts have been made to fillsuch depressions with plastic metal,but the practice seems to be a littleunreliable. Should the plastic metalbreak away, it will cause serious dam-age to the valve and possibly the pis-ton in that particular cylinder. Alterna-tively one could have the depressionfilled with weld to reduce any adverseeffects it may have on gas flow. Hereagain, this is quite a tricky job as thewhole head will have to be heated to

a relatively high temperature to avoiddistortion. The answer to all this in-decision is to leave the depression asit is unless you are bent on gettingevery little bit of power possible. Oncethe inlet port has been fully blendedand polished as in Fig. 29 we can fitthe inlet guide modified as in Fig. 30and cut the valve seat. Any sharpedges left by the valve seat cuttingoperation should be blended out byradiusing the edges. The sharp edgesof a seat can have a significant effecton the gas flow into the cylinder, es-pecially during the period when thevalve is only just off the seat. Thecareful blending of a valve seat intothe walls of the port and the roof ofthe chamber can have the same ef-fect as a cam with a faster lifting rate.The use of a cam with a higher flankacceleration rate involves higherstresses in the valve gear, whereasthe seat blending has no mechanicaldrawbacksassuming the seat widthhas not been reduced to a point whereit can no longer sustain the loads im-posed by the valve.

Rather more work is required on theexhaust ports than that needed on theinlet. The amount of grinding requiredthough, is still a lot less than neededon most heads. Grind the exhaust portto the contours shown in Fig. 31 andavoid taking metal from the tight cor-ner opposite the valve guide.

One should avoid making the ex-haust port any larger than is neces-sary to achieve a good finish. Polish-ing is an utter waste of timea goodsmooth ground finish will do the trick.With the guides machined and fitted,as in Fig. 32, cut the seat and removeany sharp corners formed. When re-moving the corners,

57

do not allow the seat width to go be-low 1/16" or short exhaust valve lifewill result. Apart from a bit of inletvalve reshaping, the head is virtuallyfinished at this stage. Just to roundoff matters, we reprofile the inlet valveto the shape shown in Fig. 23 thengive it a good polish. The importantpart of the valve reshaping is to makesure that the seat blends in smoothlywith the rest of the valve. Any suddenchanges in shape at or around theseat area cause a reduction, some-times of substantial proportions, of theflow of gas at low valve lifts.

Radius valve seats

We will deal now with the rathermore complex method of modifyingthis head using radius valve seats.Although the work may entail a littlemore skill and effort involved as com-pared with a straightforward modifiedhead, the situation can be greatly

eased by farming out certain parts ofthe work to your local motor machin-ist. Even though a greater amount ofeffort is called for to do this head inthe fashion about to be described, itis well worth it, especially it any seri-ous form of competition is envisaged.

The only point at which we are atvariance from the conventionallymodified head is the area around theinlet valve seat. In all other respectsthe head will be as for Figs. 28, 29and 31. It will be found very difficult, ifnot impossible, to use a radius valveseat with the correct radius in placeof the standard seat. The reason be-ing that the original seat has had bothadjoining surfaces machined i.e.chamber roof and port throat, and hasleft insufficient metal to form a radiusseat of the correct dimensions. Theonly practical way around this is tomake up a valve seat insert. Apartfrom enabling the

58

59

job to be done this has one other dis-tinct advantage, this being that we canaccurately form the area just belowthe valve seat. The most critical pointson any head on which one is attempt-ing to substantially improve breathing,is the area 1/2" before and 1/2" afterthe valve seat. since, for our pur-poses, there is a distinct lack of metaljust before the seat, at a point we re-quire some, the obvious answer is toput some there, hence the seat insert.To bore the head to take the insertsyou will have to call on the services ofa motor machine shop, and if you lackfacilities, he can also make up and fitthe inserts.

As you have probably guessed bynow, the inserts are not going to bejust a plain straightforward ring set intothe head. Fig. 33 shows the profileset on the insert and one should at-tempt to meet the specified dimen-

sions as close as possible. The reallycritical one is the diameter of the ra-dius upon which the valve seats. If thisdimension is out by more than 0.005'(5 thou.) the valve will not seat in itscorrect position. Before fitting the in-serts or in fact, machining the headto take them, the inlet port should befinished within 3/8" of the valve seatand the guides fitted. It is also of para-mount importance that you haveguides whose bores are on or verynear bottom limit (0.312 “ dia.). Thesize of the guides needs to be accu-rate for the pilot of the counterboremachine to locate when machiningthe head for the inserts. To get thevalve seat of the inserts accurate, inrelation to the guide, we must ensurethat both the location diameter and thevalve seat of the insert are truly con-centric. Also the counterboring of thehead

60

61

62

must be concentric within about0.001“ (1 thou.). If this is done, thevalves will lap into the seats veryquickly without undue deformation ofthe seat on the valve or insert. Whenlapping in the valves, engineers bluemust be used to check the validity ofthe seat.

After the inserts have been fitted, alittle blending with the grinder will beneeded. The final form that should beachieved is shown in Fig. 34. The use

of this type of valve seat can add upto 5 b.h.p. on top end power but thatis not the end of the story. If you areusing a hotter cam, say one thatcomes in at about 2,500 and is all offat about 7,000, then you will find thatthe use of these seats will modifythese figures to about 2,400-7,200.We are in effect, gaining in all direc-tions, having increased the power, revrange and flexibility.

63

THE T.R.4 head, from the home-tuner’s point of view, is one that isfairly easy to modify. The head is bigenough to make just about every partof the port easily accessible. The in-let port is big enough to practicallyclimb into, and the same goes for theexhaust ports to a lesser extent. It isunfortunate from the power outputpoint of view, that the inlet ports are alittle too big, but there is very little thatwe can do about that. A partial solu-tion to the problem is to avoid takingany more metal out of the ports thanis required to give a good smooth fin-ish. As with the other Triumph heads,we are plagued by the small stepwhich inevitably exists just under thevalve seat. 50% of the time this stepwill blend out when the ports are modi-fied as in Fig. 35. If the step is greaterthan 60 or 70 thou., then you just haveto live with it, or a small amount of it,even after grinding. Basically the workon the inlet port can be summed upas a little reshaping and blending anda lot of polishing to get a smooth uni-form finish. We do not want a finishakin to chrome plating, as this will onlyserve to exaggerate the fact that the

port is too big. It will also serve to en-courage fuel separation from the airbecause of the lower gas speed pre-vailing in an overly large port. The typeof finish we should go for would bemore along the lines of a vapourblasted or fine shot blasted finish. Infact if you have access to or knowsomeone who can fine shot blast theinlet ports after grinding and light pol-ishing, so much the better. If you havethe port shot blasted, then the last partof the port just under the valve seatwill need to be polished. The lengthto be polished will be about 1/4" fromthe valve seat down.

After fitting the guide, cut the seatand remove any sharp edges from theseat by radiusing off. In the interestsof retaining a valve seat of reason-able width i.e. about 30 thou., any ra-dius applied to the sharp edges of theseat should be small, in the order of40 thou. or so.

Chambers

As can be seen from Fig. 36, thereis a fair old chunk of cast iron to betaken out of the chambers. To

chapter 7

MODIFYING THE TR4 HEAD

64

65

66

67

enable reasonable uniformity ofshape from chamber to chamber oneshould make up a template fromwhich the marking out of the newshape should be done. As describedin previous Chapters, the templateshould be made from perspex for anumber of reasons, primarily though,because it is easier to make and usethan most other materials. Whenmarking out the chamber, we docome across a slight snag. Part of thesquish area on these heads is not flat.Since our template is flat and will beon the head face, we will find that mostof the surface on which we are mark-ing is falling away from the template.This means that you will have to useyour skill to judge by eye the line youare marking directly under the edgeof the template. After marking out thechamber, it is just a case of hoggingout the cast iron as shown in the draw-ing. One thing that is a little difficult toshow in the drawing is the fact thatthe undercut in the chamber wall,shown dotted, blends in smoothly withthe newly ground shape.

Ports

Inspection of Fig. 37 will show thatthere is not too much metal to comeout of the exhaust ports. Unlike mostof the other ports on Triumph engines,this one is best ground with the valveguide in place. This then brings thevalve guide flush to the roof of theport. This practice of bringing guidesflush to the port especially on the ex-haust side is one which should not bepractised without due consideration ofthe consequences. The shortening ofthe exhaust guide is usually accom-panied by a rise in exhaust valve tem-perature. In this particular case the

shortening of the guide is smallenough to have a negligible effect onthe exhaust valve temperature. Ashas been said many times before,there is no point in polishing the ex-haust port as the first few minutesrunning will completely coke up themost perfect polish. A good lump andbump free ground finish will suffice.

Apart from removing any suddenchanges in section like the bump atthe point the stem grinding termi-nates, there is little valve reshapingto do. So long as the contour changeon the back face of the valve issmooth then the valve will perform itssealing function whilst presenting theleast resistance to flow. As with theseat in the head, we should blend theunder head face of the valve smoothlyinto the seat to increase the valve ef-fectiveness at low lifts.

It is now head skimming time. Solong as we bear a few points in mind,we can get the C/R to a reasonablyhigh level. For a road car 10 to 1should be considered about as highas we want to go. For racing, we canup this to 11 to 1 since the intervalsbetween decokes are usually shorter.When skimming the head, we mustavoid making the thickness betweenthe head face and the undercut in thechamber adjacent to the inlet valvetoo thin. If we do make it too thin, thiscan lead to several undesirable con-sequences.

1. If it overlaps the bore slightly, itmay cause a hot spot, leading to deto-nation.

2. If it does not overlap the bore butinstead rests on the gasket, the pres-sure of the gasket caused by tighten-ing down the head may be just suffi-cient to cause the edge to crack andbreak away. This means

68

we have a small but very danger-ous piece of cast iron floating aroundin the relevant cylinder.

3. If the area of the head face di-rectly over the pocket has been ma-chined excessively, then when thehead is fitted we will find that part ofthe gasket is exposed. Numerousblown gaskets will be the result of this.

To get a 10 to 1 ratio we will need achamber volume of 55.5 c.c. Since we

have approximately 6 c.c. in the blockand gasket, the volume in the headwill need to be 49.5 c.c. For 11 to 1this figure will need to be 46 c.c. Toget these ratios the head when modi-fied as in Fig. 36 will need about 70-80 thou. off. When the head has beenskimmed, remove the sharp edgesfrom the chamber and it is ready toassemble.

69

CAN we say that any of the heads sofar described for the six cylinder en-gines is the ultimate within our limita-tions, imposed by using, as a startingpoint, a standard casting? Would thehottest head as described in Chapter12 be good enough to produce thepower required by our hypotheticalVitesse racer mentioned in the intro-duction? In all probability it would falla little short of the mark, but this ismerely incidental.Do we need bigger valves? The an-swer to this one is no. The valve areawe have, should suffice up to about8000 r.p.m. This means that any de-ficiency in breathing is not due to thevalve sizes employed. The ports cer-tainly are not too small for the size ofvalves used. If this is the case thenwe are left with only three areas inwhich drastic improvements can bemade. These being the chamber,valve seat and the entry direction ofthe port. If we can make substantialimprovements at these points, thenwe could be well on the way to achiev-ing that 195-200 b.h.p. that is neededto make a sure race-winner

Let us look at tile chamber design

chapter 8

THE ULTIMATE HEADfirst, and consider what happenswhen we open the valve into a cham-ber with a flat roof and walls well clearof the valve.

To do this we will look at tile effectof fluids in the port instead of air, sincefluids exhibit the same qualities asgases except for compressibility. Fig.38 (a) shows part of a port, a valveand a chamber. The fluid in the portis coloured differently from that whichis already in the chamber thus en-abling us to see the flow pattern whenthe valve is opened. Drawing (b) inFig. 38 shows the flow pattern whenthe valve is opened, and this is char-acteristic of the flow pattern through-out the opening and closing cycle. Itcan be seen that turbulence startsright on the edge of the valve seat.This has the effect of impeding theflow of gas just before the seat andthe turbulence itself is absorbing valu-able kinetic energy which otherwisecould be assisting flow into the cylin-ders.

Radius valve seats, can these help?The answer to that must be a con-servative yes. By using radius

70

valve seats we can delay the onset ofdrastically turbulent flow while thevalve is at low lifts. The radius seatscan actually increase gas flow into thecylinders by as much as 20% at lowvalve lifts. As the valve lift gets higher,so the effectiveness of the radius seatdrops off. By the time full lift isreached, the improvement gained bysuch seats is down to about 3-5%.This is by no means a small gainwhen you consider it has beenbrought about solely by a little reshap-ing. The basic problem remains as tohow to reduce turbulence as much aspossible, at least until the incominggases are well and truly in the cylin-der. Fig. 39 shows a chamber wallsection which goes a long way to solv-ing the problem. Virtually half the tur-bulence is eradicated until the basesare well within the cylinder. Tests onsuch a wall contour indicate gains asmuch as 6-8% on a normal engine

when compared with a flat chamberroof. Add this to the gains achievedby venturi ports and radius seats andwe could well be 11 % up on a con-ventional headed engine.

Down-draughting

Down-draughting the inlet portshould also produce a worthwhile in-crease in power. This could be in theorder of 3-4% when used with suit-able carburation or fuel injection. If wecombine all these ideas, the headshould look like Fig. 40.

So far everything looks quite goodon paper, but what about the problemsof making such a head. Down-draughting the head is reasonablystraightforward for any well equippedtuning establishment. It is just a caseof setting up the head in the correctposition and boring a large hole in it.Having done this, a suitable size of

71

pipe together with some sealing com-pound is pres’s fitted into the hole. Thevalve guide locating bore isremachined to remove the obstruc-tion at one end, caused by fitting thepipe, a bit of port blending is done andwe have a down-draught head. Do-ing the venturi type radius valve seatsis straightforward enough even if it isa delicate operation. This just leavesus with the chambers.

To get the chambers to the shapewe require, it is obvious that metal willhave to be put into the chamberswhich is, to say the least, a bit beyondthe scope of most home tuners. For-tunately there are firms who special-ize in welding cast iron so the prob-lem is simply alleviated. To fill thechambers, the whole head has to beheated red hot so that stress cracksdue to temperature differentials areavoided. A quick look at the relevantdrawing will reveal that it is not nec-

essary to completely fill the chambersbut only build up the areas around andbetween the valves. We will obviouslyhave to build up more than we wantto so that machining and grinding canbe done to bring it back to the correctsize. Another problem is going to con-front us in as much as filling the cham-bers is going to raise the compres-sion ratio a little higher than is reallydesirable. The answer to this is to usethe head from the 2.5 litre enginewhich is identical in every respect barchamber depth. Having filled andmodified the chamber, we will find thatthe C/R is at a reasonable level andcan be brought up to spec. by a littlehead skimming. With this type ofchamber design C/R in the order of12.5 to 1 would be beneficial.

With such a head, probably the bestsequence in which to modify the headis: (a) weld up the

72

73

74

chambers, (b) fit valve seat inserts,(c) down-draught the head and, (d)grind and polish ports and chambers.

Using this type of chamber designtogether with a down-draught port, aslightly tulip shaped inlet valve is likelyto give us better results. The shapingof the inlet valve can have a greaterinfluence on gas flow than is com-monly suspected. Tests have indi-cated that there is a family relation-ship between chamber design andvalve head profile. This relationshipcan be used only to give us a guide to

the valve profile as it is a little toovague to give us any concrete figureson which to base the valve profile.

This head design should go a longway to giving us the power output re-quired of our hypothetical 2-litre Tri-umph racing machine. By itself, it isprobably not enough to make a cer-tain race winner. There are fortunatelyother areas in which substantial im-provements can be made and weshall discuss these in the relevantChapters.

75

TO many people it seems that portmatching is something of a mystery.It is in fact quite a simple job thatneeds just a little care and patience.

The simplest method, ensuring areasonable match between the portand manifold is to match both items”to the manifold gasket. To do this, boththe manifold head joint faces arecleaned and marking blue applied toeach face. Two manifold studs arethen fitted into the head, one at eachend, and the manifold gasket locatedon them. We then scribe round theport apertures onto the head thus giv-ing us a clear indication of the posi-tion the gasket will take up. Some-times the gaskets have large clear-ance holes for the studs, which meansthat the gasket is rather a sloppy fiton the studs. This can be remediedby winding a few turns of maskingtape around each of the studs, thusgiving us a more stable location.

Once the head has been markedout, we set about doing the samething to the manifold. By using somenuts and bolts the same size as thesecuring studs or bolts in the head,the gasket can be secured to the

chapter 9

PORT MATCHING AND DOWELLING

manifold and the port aperturesmarked out. From here it is a straight-forward job to cut away the metal onboth the manifold and gasket up tothe previously scribed line.

We have, of course, made the as-sumption that the ports in the gasketsare the same size as the ports re-quired in the head. Most manifoldgaskets are about 3/32" larger thanthe port sizes which in all the caseswe have covered remain standardsize as far as the inlet are concerned.This means that ideally the line thatis scribed for working to must be 3/64”in from the edge of the gasket. Theport size at the joint face between themanifold and head is not critical within1/64" so when we say the port shouldnot be enlarged, it should not be en-larged any more than is necessary tomatch it up. This method of portmatching is the simplest but the ac-curacy obtained is limited by clear-ance on the manifold location studs.This clearance allows a certainamount of movement which directlyaffects the lining up of the ports. Al-though

76

this method is not super-accurate, itdoes leave things far better than theyare as standard.

Dowelling

For a super-accurate port match-ing job, we have to be a little moresophisticated about things. Firstly weshall require some 1/8” dowel pinsThese can be made up from a lengthof 1/8” dia. silver steel as this is veryaccurately sized. Silver steel inci-dently, is available through most con-cerns dealing in engineers’ tools andis commonly sold in 13" lengths. Fromthe silver steel we make up somedowel pins about 3/8” - 7/16” long.These should then have their endschamfered or radiused. The numberof dowels required will depend on thetype of manifold being fitted. A one-piece manifold will require two dow-els; a two-piece manifold will requirefour dowels; each part of the mani-fold requiring two dowels to locate it.

The next step is to fit the manifoldStuds in the head and bolt the mani-fold in place with two or three gas-kets between the head and manifold.Be sure to line all the gaskets up withone another. To take up any play onthe studs we can, as before, usemasking tape. With the manifoldbolted securely in place, drill two holesin a convenient position in each com-ponent part of the manifold. Normallythe best place to drill such holes isabout 1/4" away from the fixing studs.The size of drill for the hole is 0.110"and the drilling should go about 3/8"into the head casting after passing

through the manifold and gaskets. Donot remove the manifold at this stage,drill all the holes that are needed inone go. Next, using a worn 1/8”reamer, one that is about 0.001“ un-dersize, ream out the holes throughthe manifold into the head. Inciden-tally you may find that in some casesi.e. Weber manifolds, that the drill orreamer length is insufficient to reachthe base of the manifold without foul-ing some other part of the manifoldwith the drill chuck. This situation canusually be overcome by fitting the drillor reamer into a slim pin chuck andthen holding the pin chuck in the drill.

Once we have reamed the dowelholes with the undersize reamer, wecan remove the manifolds from thehead. We now fit the dowel pins intothe head. Providing you selected yourreamer at 0.001" undersize, the dow-els will be a light drive fit in the head.It is not a good idea to have the mani-folds a light drive fit on the dowels, sousing a new 1/8” reamer, ream out themanifold holes. If the job has beendone right, we now find that the mani-folds are a snug push fit on the dow-els and there is a complete absenceof sloppiness.

Since we now have a really accu-rate location for our manifolds andgaskets we can tackle fhe port match-ing procedure as described previ-ously: The dowels will, however, takethe place of the studs when markingout the ports to their relevant gasketapertures. The adoption of thismethod enables port matching towithin about 0.007” when done care-fully and that cannot be bad.

77

THE sole function of springs, rockers,pushrods and tappets is to convey themotion imparted by the cam to thevalves. As such the valve train, includ-ing the camshaft, must be regardedas a whole. Any mechanism is boundto suffer from flexure of various com-ponents. Any flexing which is broughtabout by the relevant dynamic or staticloads imposed, makes the job of thecamshaft that much more difficult.The cam designer goes to a greatdeal of time and trouble to produce acam profile which will minimize theeffects of vibration, shocks and flex-ing in the valve train. Because of thenature of the valve train in the normalO.H.V. engine, he is fighting a one-sided battle. We must consider, whenmaking any modifications to the valvetrain as a whole, whether or not weare making the situation worse as faras loads and flexure factors are con-cerned. The first golden rule to beapplied is: Never use valve springsany stronger than are needed to dothe job. If you do, it will cost you power.You must consider at what r.p.m. yourpeak power is likely to occur, and thenselect valve springs which will allow

chapter 10

SPRINGS, ROCKERS, PUSHRODS AND TAPPETS

the engine to run 10-15% over theserevs. Since the camshaft is the maininfluencing factor controlling the pointat which peak power occurs, then weshould select valve springs land camtogether.

If substantial improvements havebeen made in the breathing ability ofan engine, but the cam remains stan-dard, the situation can sometimes callfor slightly stronger valve springs. Thismeans that we cannot use the prin-ciple, at least in early stages of tune,of selecting cam and springs together,as a hard and fast rule. However,since we are dealing solely with thelarger Triumph engines, we can be farmore specific about things. All theTriumph cars with which we are deal-ing have sufficient spring pressure tocontrol valve bounce up to highenough revs when using the standardcamshaft. This even applies to en-gines which have had substantial im-provements made in the head, inletand exhaust side of things. Some-times one can gain a false impres-sion in as much as the engine feelsas though it can usefully rev higher,

78

but quite frankly one is off the bestpart of the power curve and you wouldbe better off in the next gear up. Allthe sixcylinder Triumph engines canrev to 6,300 or over on standardsprings. Without making a camchange, it is unlikely that the point atwhich peak power occurs can beraised to much more than 5,800 r.p.m.This means that fitting strongersprings with a standard cam is awaste of time and serves only to re-duce the power output by raising theinternal friction level of the engine.

Cams and springs

When we do change to a hottercam, then we shall definitely needsprings to go with it. Running the en-gine to valve bounce revs is a prac-tice to be avoided as much as toostrong a spring set-up. Valve bounceoccurs when the spring pressure isinsufficient to keep the cam followerin contact with the cam at the revsprevailing. This means the cam fol-lower may leave contact with the camjust after the toe-peak lift point-of thecam and may not touch again until theheelbase circle. This sort of use im-poses terrific shock loads on the com-ponents of the valve train. It can leadto premature demise of the cam fol-lowers and cam lobes. While the tap-pet is off the cam follower, the valveis being brought down onto its seatsolely by spring pressure. Instead ofbeing gently let down into its seat bythe closing ramp of the cam, it issmashed down by the full force andspeed that the spring can muster. Theseat, valve and spring are not goodenough shock absorbers to absorbthe full energy of the rapidly movingvalve, so the valve promptly bouncesback off the seat. The loads andspeeds involved are so high that thevalve may bounce off the seat two orthree times before it finally comes torest ready to go through the next

cycle.All this explanation is leading up to

one thing. When buying a cam, con-sult the cam manufacturer as to whatsprings should be used. Let me quotean example. S.A. H. do five differentcam grinds for the six cylinder en-gines, and each cam profile has aspecific set of springs to go with it.The same also applies for the twocams S.A.H. do for the four cylinderengines.

Having lightly touched on the sub-ject of springs, let us turn to the rock-ers. After a head has been skimmed,one can sometimes find that there isinsufficient rocker adjustment left.There are two ways of overcomingthis problem. We can either shortenthe push rods by the same or similaramount taken off the head or raise therocker shaft to compensate. I person-ally am not in favour of the secondmethod, although it is the simplestmeans of solving the problem. Ideallythe rocker should be horizontal whenthe valve is at the half lift point i.e. therocker will swing an even amountabove and below the horizontal. If weskim the head then, assuming at thispoint there is sufficient rocker adjust-ment, we will reduce the angle therocker makes to the horizontal whilethe valve is still closed. When thevalve opens the rocker will passthrough the horizontal position beforethe half lift point is reached. Thismeans the total angular displacementfrom the horizontal is increased. Letus go back to the situation wherepacking shims under the rockers isrequired to allow adjustment. We findwhen the shims are fitted, we reducethe initial rocker angle even more thanwith just the skimmed head. Therocker reaches the horizontal positionalmost as soon as the valve is

The pushrod can be considered asthe weakest link of the chain in mostO.H.V. engines. This is not from thepoint of view of strength,

79

80

off the seat, instead of the idea pointat half full lift. Also the maximum anglefrom the horizontal has been in-creased and this is undesirable forseveral reasons. Firstly the rubbingmotion between the tip of the valvestem and the contacting rocker faceis increased which in turn increasesthe wear rate. From this stems the factthat tappet clearances are likely toneed more regular adjustment. Sec-ondly the side forces on the valvestems causes a greater rate of valvestem and guide wear. Thirdly, any in-crease in friction is undesirable in anyengine, especially one intended forhigh performance. We need not runaway with the idea that shimming therockers is totally disastrousall thepoints raised merely constitute smallbut unwanted side effects.

Unlike shimming, shortening of thepushrods does not have any un-wanted side effects. By shortening thepushrod, we allow the rocker to con-tact the valve stem through the opti-mum angles i.e. an even angle ofswing above and below the horizon-tal. The horizontal position will, ofcourse, coincide with the half full liftvalve. The shortening of the pushrodshas also given us a small reductionin valve gear weight, and every littlebit helps. The pushrods ideally shouldbe shortened by the same amount ofmetal that has been taken off the headthus restoring the condition which pre-vailed originally. When the pushrodsare shortened, the original form mustbe remachined on the end and we will,of course, shorten from the cam fol-lower end and not the rocker endcomponent which receives continualabuse from the camshaft, one shouldcheck that (a) it is a good fit in its boreand (b) that the face but from the point

of view of flexibility. The pushrod issimply a load bearing column. Assuch, it functions reasonably well,while it is dead straight. If there is theslightest bend in the pushrod the flex-ing it experiences during use will goup out of all proportion and the mo-tion of the valve will bear only a vagueresemblance to the motion dictatedby the cam. As you have probablygathered by now, the moral is to checkeach pushrod for straightness.

Tubular pushrods

Although none are commerciallyavailable at the time of writing, I itwould appear that there is scope forthe use of tubular pushrods. It wouldappear that we have ample roomdown the pushrod holes to accommo-date tubular pushrods approximatelytwice the diameter of the standarditems. This is the sort of thing neededfor our, as yet , hypothetical racer.Since a tubular pushrod of similarcross-sectional area would be farstiffer than the standard items, wecould usefully employ a higher flankacceleration on the cam profile. Thisfaster rate of lift would enable betterbreathing and hence more power.

Consideration of the tappets or camfollowers brings us to the last com-ponent in the valve train before we getto the camshaft. The camshaft will bedealt with in a chapter of its own as itdeserves more than a passing men-tion. There is, however, little that canbe said about tappets except that theyare hard working components andshould be treated with respect. Sinceit is a which bears on the cam is notpitted or concave. If the face is at allconcave, then the valve opening mo-tion is adversely affected.

81

DROPPING in a larger motor is asimple and safe method of increas-ing a car’s performance, but it is diffi-cult to try to put forward every con-ceivable combination of bits andnearly impossible to foresee everysnag that is likely to arise. Howeverthe information here should give ei-ther food for thought or a good guideas to what should or can be done withthe least complications.

Vitesse 1600

We will deal with the 1600 Vitessefirst as this is the most likely one toreceive attention in the form of capac-ity increases. There appears to be nogreat problems which is as one wouldexpect, in bolting the Mk. 1 2-litreVitesse engine straight in. On theother hand fitting the Triumph 2000engine is not quite so straightforward.The principal difference in the blockarises in connection with the enginemounting points. The Mk. 1 Vitesseengines have, cast on the left handside when viewed from the front, alarge boss projecting some 2-1/2"from the main body of the block. Thisboss has four drilled and tapped holes

chapter 11

ENGINE INTERCHANGEABILITY

in it, one at each corner, and is thepoint at which the Vitesse enginemount fits.

Triumph 2000

The Triumph 2000 enginemounts are situated on the front ofthe engine and are in the form of aplate between the timing chain coverand the block. The early Triumph2000 block, unlike the Vitesse block,does not have such a large boss onthe side of the block. The part of theboss present has no threaded holesto permit securing of the enginemount. This means that if you shouldget hold of a Mk. 1 Triumph 2000 en-gine, you will have to (a) drill and tapthe block and (b) make a metal spacerof approximately 1-1/4" thickness tomake up the space between the blockboss and the Vitesse engine mount.Since the boss on the block is muchsmaller, we must be very careful notto drill and tap the block too deeply,otherwise we shall break through intothe inside.

If we resort to a later engine, thatis after late 1966, then we find that

82

some rationalization was broughtabout at the factory and all blockswould appear to be the same. Thismeans that by using the later engine,we can, without a great deal of effort,transplant any engine into any carwithin the range. There may be occa-sions when parts outside of the en-gine need changing to retain partscompatibility, but there does not ap-pear to be occasion to use bits otherthan off the shelf Triumph parts. Thebiggest expense when fitting the lateengine into a pre ’66 car other thanthe engine itself, would appear to besome new manifolding because, youwill remember, the later engine has adifferent head.

If you have the Mk. II G.T.6 orVitesse, then it becomes unnecessaryto change the whole engine to get thecapacity up to 2.5 litres. The later 2-litre engines have the bigger mainsjournals which are, in fact, the samesize as those on the TR 5 or 6. Thismeans that we need only change thecrank rods and head for those of thebigger engine.

Incidentally, whilst we are on the

subject of blocks, the Triumph 2000engine is only a bored out version ofthe 1600 Vitesse engine. When the2000 block was brought out, the boreswere cast to allow for the bigger sizeemployed. If you should try boring the1600 out to 2000 c.c. you will just endup with a scrap block, so do not try it.

Since the engines are, in the main,bored or stroked versions of eachother, we get virtually no problemsassociated with weight. Usually drop-ping in a bigger engine has certaindisadvantages connected with it, suchas making the car front end heavy.Here the problem does not arise sinceall the engines have weights within afew pounds of each other. At facevalue, increasing the engine size is agood way to get more performance.The cost of such a project, however,is a little on the high side in terms ofb.h.p. gained per pound spent, as-suming new parts are purchased. Tocounter this, any subsequent im-provements made, result in a greaterpower increase on the larger enginesthan the smaller ones.

83

THERE is very little we can do to in-crease the bottom end strength onthese engines as far as componentchanging goes. This means that wehave to resort to methods which willgive the greatest reliability using thestandard parts.

Tuftriding

To start with, it is a good idea, if weare to use the maximum rev potentialavailable, to have the crank and rodstuftrided. For a very reasonable priceyou can get your own rods and cranktuftrided. This process has the effect,as you have probably guessed, of in-creasing the toughness of a steelcomponent. By doing so we find thatit is less likely to break through fatigueat sustained high revs. It also enablesus to raise the rev limit before catas-trophe occurs, by 5-7%. After com-ponents have been tuftrided they arecovered in a grey film. This must beremoved from all bearing and locat-ing surfaces by polishing. Some “600”grit wet and dry emery paper will dothe trick nicely, but be sure to removeevery trace of grit before using thecomponent.

chapter 12

STRENGTHENING THEBOTTOM END FOR COMPETITION

Shot peening

Another way in which we can in-crease the fatigue life and the ultimatestrength is by polishing or shot peen-ing. The surface flaws and Imperfec-tions reduce the strength of a com-ponent by a fantastic amount. If wecould remove every surface flaw ona steel component down to the mo-lecular level, the strength of the com-ponent almost doubles. Unfortunatelyremoving flaws down to the molecu-lar level is virtually impossible. Evenif we could do so, the bombardmentof air molecules is sufficient to ren-der our perfect finish imperfect, butmake no mistake about it, the polish-ing of the engine’s vitals does makea worthwhile difference, even if thefinish is imperfect. A well polished orshot peened rod can have a fatiguelife easily double of that of a standardcomponent. This is not to say that itsstrength is doubled. The differencebetween breaking and not breakingdue to fatigue can be quite small. Thepolishing or shot peening may haveonly given us a 5% marginstrengthwise over the standard item,but at a given r.p.m. it is enough to

84

make the difference.I should think we all know how pol-

ishing is done, but far less is knownabout shot peening. An object is shotpeened by firing small glass or steelballs at the component. These ballshave a relatively high surface finish.They strike the component at a highenough speed to cause a smallcurved indentation and in doing so,impart some of their high surface fin-ish onto the component. This has theeffect of eradicating the creviceswhich cause stress points. Fig. 41shows the surface finish under mag-nifications of (a) a forged surface (b)a polished surface and (c) a shotpeened surface. From this you cansee that the shot peened surface hasdone as much to remove stress pointsas polishing, although the actual ap-pearance of the finish is somewhatdifferent. It is advisable to give thecomponents a little attention before

they are short peened. For instanceone should remove all forging marksand try as much as possible to smoothout the surface all over.

If we are going the whole hog bytuftriding and surface finishing, be itpolishing or shot peening, things haveto be done in a certain order. Thecomponent must be prepared prior totuftriding by grinding off any forgingmarks and generally cleaning it up. Ifthe final surface operation is polish-ing, the rod is best polished beforetuftriding as after the processing wemust avoid any metal removal. If thecomponent is to be subsequently shotpeened, then we need not be so fussyover the finish prior to tuftriding.

A word of warning here would notbe out of place. Do not send any bitsfor tuftriding if at any time they havebeen bent and had to be straightened.The toughening process will causethem to revert back to their bent state.

85

After toughening, all componentsshould be checked to see that theyhave not distorted as this sometimesoccurs. Small amounts of distortioncan be remedied by normal straight-ening procedures, but if too badly dis-torted, the relevant component shouldbe replaced, by another toughenedone. The little end bushes in the rodsare always badly eroded by tuftridingand will need replacement after pro-cessing.

With the bottom ends fullyprepared, we should get rev limits inthe order of 8,300 for the 2-litre Mk.11 sixes, and about 7,200 for the TR4

and 4A engines. Due considerationshould be given to the 2.5 litre six,because of the longer stroke, and itis probably wise to limit them to 8,000or just under. The early 1600 and 2-litre engines, because of their smallmain bearings, should not be run inexcess of 8,000 revs. There are en-gines of similar size that will rev higherthan this in safety but quite franklythese Triumph engines have enoughrevs for our purposes. To get a peakpower which needed more than 8,000r.p.m. we should have to resort tosome very sophisticated tuning in-deed!

86

87

88

89

The con-rods of an engine are usu-ally the first items to get attentionwhen the time comes for lightening.In the case of the Triumph rods, thereis little we can do to vastly reduce theweight. Slight weight reductions will,of course, be achieved by grinding offthe forging marks and generallyrounding off square edges. Anyweight reduction must be consideredworthwhile if we are going all out onthe engine, but for all normal applica-tions it is not worth the great deal ofeffort involved.

Some of the Triumph pistons canbe lightened by cutting away part ofthe skirt as in Fig. 42. One can easilyidentify which can be lightened andwhich cannot by the fact that somepistons already have this part of theskirt cut away. Those that are alreadycut away should be left as they are.Do not shorten the pistons as with thebore sizes quoted elsewhere in thebook, the pistons will be allowed torock too much in the bores.

Rockers

The rockers for the “sixes” can use-

fully receive some attention to reducetheir moving mass. These should bereshaped as in Fig. 43 and finally pol-ished to reduce the effects of surfacestress points. When grinding, onemust avoid touching the surface of therocker which bears on the stem of thevalve. Any deviation of the true curvecaused by wear or otherwise, resultsin an error of valve motion. The valverockers for the four cylinder enginecannot effectively be lightened anymore than they are, but a good pol-ishing session on them would cer-tainly not go amiss.

Cam followers

The cam followers can be lightenedby machining out the bore as shownin Fig. 44. The size to bore the camfollowers-dimension A-varies depend-ing on the size of cam followers in theengine. The 0.687" dia. tappet usu-ally found in the 1600 Vitesse and theMk. 1 2-litre engines can be bored to0.590" dia. The larger tappet found inthe later engines is 0.800" dia., andcan be bored to 0.700" dia. The onesfor the four cylinder

chapter 13

LIGHTENING ENGINE COMPONENTS

90

91

92

engines which are larger at 0.937'dia., can be lightened by boring to0.840". The boring of the cam follow-ers to these sizes will give a weightreduction in the order of 20%.

Another worthwhile weight savingcan be had by reducing the thicknessof the locking nut on the rocker ad-justing screw to half of its originalthickness. This usually results in farmore of the rocker adjusting screwprotruding from the locknut than isnecessary. Once the tappets havebeen adjusted, we can see exactlyhow much of the rocker screw is ex-

cess. It is then shortened by anamount which leaves enough to puton a plain shank and a screwdriverslot. The advantage of lightening per-formed on the end of a rocker as op-posed to lightening near the pivotpoint, is that it has the greatest effecton the reduction of reciprocatingweight and is therefore most useful.Although it does not come into thecategory of lightening of standardcomponents, the making up of alu-minium spring retainers should bementioned. By using aluminium in-stead of steel, we can cut the spring

93

retainer weight by 50% which is, youmust admit, a fair amount. We can-not make the aluminium retainers,size for size, the same as the steelones, as they would not be quitestrong enough. To compensate for thelower ultimate strength of the alu-minium, we should make the retain-ers thicker on the face that the outerspring beats against see Fig. 45. Onlygood quality high tensile aluminiumalloy such L65 should be used forthese retainers, this has a strength inexcess of 25 tons per square inch.

Flywheel

The standard flywheel is, on the sixcylinder engines, good for giving asmooth tickover, but for a tuned mo-tor it is unnecessarily heavy. The fourcylinder engines also have a heavyflywheel. For these engines, you canhave one of two different flywheelsdepending on the type of clutch fitted,the one being heavier by far than theother. To lighten the flywheel, it is sim-ply mounted in a large lathe and ma-chined as shown

94

for the relevant flywheel in Fig. 46.Practically any motor machine shophas a lathe large enough to tacklesuch a job, so there should be noproblem getting it done. It must bepointed out that a lighter flywheel nei-ther increases the power nor makesthe car faster. It does, however, allowthe car to accelerate faster becauseof the reduced mass which the en-gine has to speed up. The lower gearthe car is in the greater the effect ofthe reduced flywheel weight. To clarifythe point a little, let us look at a simpleexample.

Let us assume that we have re-duced the effective weight of a fly-wheel by 10 lb. While the car is inbottom gear the engine r.p.m. to driv-ing wheel r.p.m. is 16 to 1 i.e. the en-gine turns 16 revs to the wheel’s one

rev. The 10 lb. flywheel weight reduc-tion is equivalent to reducing theweight of the car by 160 lb. that is 16x 10 lbs. When we change to secondgear which, we will say, is about 12 to1 overall ratio, the gain, because ofthe lighter flywheel, will be 12x10 lbs.which is 120 lbs. By the time we getto top gear, the effect of the lighterflywheel will only be about the sameas lightening the whole car by 4x10lbs. or 40 lbs. With the exception ofone of the TR4 flywheels the effec-tive weight saving will not-be as greatas 10 lbs. A more likely figure is be-tween 6-8 lbs., but this is enough tomake a noticeable difference. By wayof a bonus, the lighter flywheel alsoenables snappy gear changing whengoing down the box.

95

THE camshaft is a component whichis often taken too much for granted.The designing of a good camshaft isprobably one of the most difficultthings within the internal combustionengine. For a camshaft to have a rea-sonable life, yet produce the requiredbreathing characteristics for a highperformance engine, the cam profilehas to be carefully calculated. Theprofile must be such as to limit shocksand vibrations, and keep the inertialoads to a bearable level. It is only bycareful control and accurate manufac-ture of the cam profile that the de-signer can come to terms and limitthe undesirable elements of the cam.For this reason we should never usea cam with worn lobes as we couldbe imposing stresses or shocks farhigher than were ever intended.

How does one go about choosinga suitable cam ? Firstly we must de-cide at what point we need the power.For fast road work and town driving,we should use a cam that can rundown fairly low revs and still give uspower. This means the timing is offairly short duration and there is onlya small amount of overlap. If your

chapter 14

HIGH PERFORMANCE CAMS

town driving is of a limited nature andthe car is mostly used on open roads,we can afford to lose a little at thebottom end of the rev range to gainpower at the top end. For this appli-cation we can go to a more hairy cambut still one that retains a sensibleamount of flexibility. For rallying,autocrossing or for the man who hasto use the daily road transport for theweekend race meeting, we can pullthe stops out a fair bit and install acam which will go between 2,500 upto 6,500 or so. For circuit work a camgiving power between 3,000 to 7,000would be a good choice.

Not only do we have to consider theapplication of the car when selectinga cam, but also we must considerwhether it is reasonably compatiblewith the rest of the engine modifica-tions. For instance, a full race camwould be a bit of a waste of time on a1600 Vitesse, if the standard Solexcarbs were still retained. Before fit-ting a cam that is vastly different tothe standard one, you should defi-nitely reach a reasonable level of so-phistication in other

96

quarters such as head, carbs andexhaust system.

With the TR4 and 4A, wecannot go too wild on cam timing be-cause of a rev. limit, which even witha fully prepared bottom end, is only alittle over 7,000 strictly speaking, wecannot really use a cam that gives apeak power any higher than about6,500 r.p.m. This means that there isnot such a vast difference betweenthe standard cam and a full race oneas there is with some cars. Since thestep from standard to full race is a littleless than usual, there are less camsto fill the gap between road and raceprofiles which means our choice islimited. Because of the relatively lowrev. limit, most cam manufacturersproduce only one or two profiles -fromwhich to choose for this engine. Thestandard TR4 and 4A cam timing is afairly modest 17/57-57/17 with a liftof around Y.”. For better breathing up

at the top end without any appreciabledrop in the lower rev range, the S.A.H.26 cam can be fitted. This has slightlymore duration than the standard cam,the timing figures being 22/62-62/22.Total. valve lift is up to 0.432". Thiscombination of lift and timing makesthe cam ideal for fast road work andthe occasional competition meeting.A cam which does a very similar jobto the S.A.H. item is made by PiperCams. The Piper cam has slightlylonger timing but less lift, the figuresfor these being 24/64-64/24 with0.387" lift. V. W. Derrington can sup-ply a cam which they say is designedto give the best torque characteristicsin view of the relatively low maximumsafe revs (7,000) of this engine. Onthe face of it, this cam should repre-sent a good bet for the man who useshis race machine on the road, as trac-tability does not suffer too much. Thetiming for the Derrington cam is 30/70-

70/30 with a lift of 0.420". Pipers alsodo a cam with similar timing and lift tothis one. Any cam past this stage defi-nitely starts to chop out the low endperformance, but if you intend to usethe car for any form of serious com-petition, the revs must be sacrificed.

Manufacturer Timing Lift No.Piper 30/70-70/30 0.435' 1

35/75-75/35 0.390" 236/76-76/36 0.406" 345/85-85/45 0.435“ 433/71-71/31 0.406 “ 5

S.A.H. (26) 22/62-62/22 0.388" 6(46) 40/60-60/40 0.398" 7(57) 50/70-70/50 0.425" 8(47) 40/70-70/40 0.428" 9(357) 33/71-71/33 0.395" 10(387) 38/72-75/35 0.382" 11(578) 52/78-78/52 0.410“ 12(467) 46/74-78/42 0.385" 13

V W Derrington 30/70-70/30 0.435" 1435/75-75/35 0.390" 15

Racing

For racing we must go for theS.A.H. 47 cam (43/76-76/43 with a0.480" lift). This cam must be consid-ered as a full race cam, and if used ina road car, can be just a little tiresome,especially in traffic. The useable rev

97

range with this cam is approximatelybetween 3,000 and 7,000 which is thelimit as far as the 4 cylinder Triumphengines are concerned.

A far wider range of cams is avail-able for the six cylinder engines thanthe four cylinder ones. This widerchoice allows a closer tailoring of theengine to one’s needs. The easiestway to cover these cams is to list areasonable number of them and thendiscuss any special merits that theymight have.

For a good road cam in a 1600 orMk. 1, 2000 motor, cam numbers 2,6 or 15 are a good choice. The timingfigures are not too drastic for road useand the lift is quite adequate for thestandard valve sizes. We can lift avalve too far and there is no point ingoing higher than about 0.30" of thediameter of the valve. Since the stan-dard size of valve in a 1600 or Mk. 1

2000 engine is 1.3", a quick calcula-tion will reveal that we need a lift of0.390". The 0.390" lift given by thiscam is therefore close to the mark. Itis also interesting to note that this typeof cam can be used beneficially in the2.5 litre Lucas fuel-injected engineswithout having to change the fuel me-tering cam. The S.A.H. 357 (No. 10)and 578 (No. 12) and the Piper cam(No. 5) also save this modification,which is very useful when you con-sider that reprofiling the fuel ram takesa good few hours on a dynamometer.The 357 cam is the sort of cam thatstarts running right around the 1,500revs or so, and it is quite roadable.The 578 on the other hand, is a raceprofile and needs upwards of 3,000revs just to get going. The best revrange for this cam is between 4,000and 7,000. Cams number 1 and 14are

98

also good touring cams, giving a use-ful increase in power without killing offa noticeable amount of power at thebottom end. To make the best use ofthese cams, they should be used inthe Mk. 11 engines, or Mk. I enginewith a bigger inlet valve, Cams num-bers 3, 7 and 11 make a good com-promise for road/competition use inthe 1600, 2000, or carburated 2.5 li-tre engines. Since the bigger enginesbring the r.p.m., at which the camcomes in down, we can afford to go alittle further on cam timing for road usebefore it becomes too intractable. Forinstance, as a road/race cam for acarburated 2.5 litre engine, the 46/74-78/42 cam (No. 13) might be a goodchoice. A good example of this wouldbe the fitment of this cam into the TR250 which is the carburated versionof the TR 5. The remainder of thecams, including the S.A. H. 578 camalready mentioned, can be consid-ered full race cams.

Fitting

Once you have decided on a par-ticular cam, then it is imperative thatit is fitted correctly. To fit the cam cor-rectly it must be timed by using a de-gree plate and a dial indicator. If thecam is not correctly timed then we canbe throwing a fair amount of poweraway. Just installing the cam andbringing up the timing marks is, inmost cases, not good enough. Toensure that the cam will function cor-rectly, the following procedure shouldbe adopted when fitting it.

Using a dial indicator with its proberesting on top of the number 1 piston,establish T.D.C. When bringing thepiston up to T.D.C. turn it in the nor-mal direction of rotation and applythumb pressure to the top of the pis-ton to take up bearing clearances. In-

sert the camshaft so that the inlet andexhaust cams on number 4 cylinder(for 4 cylinder engines) or number 6cylinder (for 6 cylinder engines) arerocking i.e. the inlet is just openingand the exhaust is just closing (seeFig. 47). This will mean that the camsin number 1 cylinder will be such thatboth valves are closed which will, ofcourse, be the situation prevailingwhen number 1 is firing, and on thepower stroke.

The next step is to fit the sprocketstogether with the timing chain. Thedegree plate is now bolted to thecrankshaft, and a pointer fixed to theblock is set on the zero degree markof the degree plate. The situation isnow as follows: we have the crank setso that number 1 piston is at T.D.C.and our datum from this is set on thedegree plate. We have the cam in-stalled in the approximate correctposition within about +/- 150 (if yourjudgment of the positioning of the camlobes is anything like, that is) and thecamshaft connected to the crank. Weare now in a position to run through atiming cycle on one of the cams, wewill say, for instance, number 1 inletcam. To do this we attach a long stemto the dial indicator and seat it on thecam follower of number 1 inlet cam,see Fig, 48. Assuming the engine tobe still at T.D.C. on number 1 cylin-der, rotate the crank in the reverse ofnormal rotation about 1800 i.e. aboutB.D.C. The inlet cam follower shouldnow be on the base circle of the cam.Set the dial indicator to read zero whilethe cam follower is on the base circleof the cam. Turn the crank in the nor-mal direction of rotation. As it isturned, at some point you will see thedial indicator slowly moving round thescale indicating that the cam is nowon the

99

100

clearance ramp. As the crank isturned still further, the rate of motionof the dial indicator needle will quitesuddenly increase. This shows thatthe cam has started the lift cycle. Turnthe crank back and establish the pointat which the lift cycle starts, this be-ing the point at which rapid motion ofthe dial indicator needle starts. Thispoint can also be established by di-viding the rocker ratio into the valveclearance. This then gives the heightof the clearance ramp on the camThis point is quite easily seen, as therate of motion of the dial indicatorneedle goes up by 2 or 3 times thatcaused by the clearance ramp. Hav-ing established the opening point ofthe valve, check the number of de-grees before T.D.C. that this openingpoint occurs, and compare it with thequoted cam timing figures. By com-paring the actual figures existing, withthe correct figures, we can determinethe exact error present. Once the er-ror has been noted, turn the engineback to T.D.C. on number 1 cylinderand remove the timing plate. Removethe sprockets and chain to make thenecessary timing corrections. If thecam is too far advanced i.e. the inletis opening early, the cam will need tobe turned in the opposite direction tonormal rotation i.e. anti-clockwisewhen viewed from the sprocket endof the engine. If it is too far retarded,then turn the cam clockwise. Move thecam sprocket in the chain around therelevant number of teeth (usually oneor two) to line it up with the fixing holesin the cam and the keyway on thecrank, and refit it. Recheck the tim-ing. By this time the error should beno more than one tooth of the camsprocket.

If you look closely at the camsprocket, you will see four securingholes which are equally spaced butoffset from the centreline of thesprocket teeth. By juggling the

sprocket around, we can make tim-ing corrections down to a quarter of atooth pitch. This means that we canget our timing accurate to a little over+/- 20 at the crank. Assuming we areat the point where the difference inthe required timing, and the timingexisting on the engine is no more thanone tooth, i.e. 8.6 cam degrees of17.2 crank degrees, we can adapt thefollowing procedure to correct it :

Error at crank Error at sprocket 17.20 1 tooth (8.60)

RemedyRemove sprockets and timing

chain, unmesh the sprocket and turnit one tooth in the relevant directionwithin the chain. Turn the cam a simi-lar amount and refit sprockets andchain.

Error at crank Error at sprocket 12.90 tooth (6.450)

RemedyRemove sprockets and timing

chain. Turn the cam sprocket back tofront and rotate it through 900. Refit itinto the chain and offer up to engine.Turn the cam to align up holes insprocket. Refit the assembly.

Error at crank Error at sprocket 8.60 1/2 tooth (4.30)

RemedyRemove sprockets and timing

chain. Unmesh the sprocket from thechain and turn it 900 then remesh it.Offer it up to the engine, turn the camto line up the fixing holes and refit thechain and sprockets.

Error at crank Error at sprocket 4.30 1/4 tooth (2.150)

RemedyRemove sprockets and timing

chain. Turn the sprocket back to front.

101

102

Refit it into the chain and offer up tothe engine. Turn the cam to align fix-ing holes and refit chain and sprock-ets.

Looking at the chart you can seethat our incremental adjustment at thecrank is 4.30. The maximum errorfrom the required timing with suchsteps of adjustment will be half of 4.30.This means you must adjust to thenearest quarter tooth to the requiredtiming. The maximum final error willoccur when the error we are adjust-ing for, falls exactly half way betweena quarter tooth pitch, i.e. 2.150. If youhave a choice of two settings which

are equally spaced either side of thedesired setting, then choose the onemost retarded of the two as a delay ininlet valve closure is better than anearlier opening. Once the cam is cor-rectly installed, it is wise to put on twoof your own timing marks so that youwill not have to repeat the cam set-ting when the time for rebuildingcomes. Incidentally, one can obtain acam timing plate from S.A.H. or a 3600

protractor can be adapted for such apurpose, A dial indicator can be pur-chased at shops dealing in engineers’tools and is a worthwhile investmentto any engine builder.

103

THE Solex carburetters fitted to theearly 1600 Vitesses do not allow theengine to breathe as well as it coulddo even in standard form. If, for somereason or another, you have to stickwith them, then a few hints may beuseful.

If the head has been modified, themain jet size will need to be increasedby about 0.3 to 0.5 of a m/m. Sec-ondly, the very first Vitesses had fixedjet carbs on the accelerator pump. Onthe later 1600 cars this pump was dis-carded to assist hot starting. The per-formance was seemingly unchangedby such a move. If you have the earlymodel fitted with accelerator pumps,then an improvement can possibly begained by discarding them. By far thebest method is to discard the carbscompletely and fit the later twinStrombergs as these have a greaterbreathing capacity and allow moremods to the engine before they be-come inadequate. The twinStrombergs were fitted to the last ofthe 1600 Vitesses and the Mk. 1 2-litre Vitesses and G.T.6’s. If you canget the carb and manifold setup fromany of these cars for the early 1600,

it can be bolted straight on. If the carbsare off one of the 2-litre engines, theywill, of course, need reneedling. In factif anything has been done to the en-gine, the needles will inevitably needchanging to some which will give thecorrect fuel/air characteristics throughthe rev. range. It is very difficult if nottotally impossible, to state whatneedle will be required since it willdepend on what other componentshave been modified. If we allowed forall combinations of various parts, wecould end up with a needle list bigenough to make a small book. At thisstage we need not worry too muchabout this as there are ways andmeans of sorting carburation to get itspot on which will be gone into in alater Chapter.

The next stage of carburation im-provement is to fit triple S.U.’s whichare available through V.W. Derrington.These give vastly improved breath-ing over the Solex carbs and are dis-tinctly better than the twinStrombergs, not, might I add, throughany deficiencies with the Strombergcarb., but from the fact that threeS.U.’s are better than

chapter 15

CARBURATION FUELINJECTION AND MANIFOLDING

104

two Strombergs.By using triple S.U.’s instead of the

standard set-up on carburated 1600or 2000 engines, we can expect apower increase of 15%-20%. As isusual with a good S.U. set-up, the fuelconsumption does not go up out ofall proportion when compared to thepower gained. In fact, driven at nor-mal road speeds, triple carbs seemto give better consumption figuresthan an engine with standard carbs.

Next step up the ladder as far ascarburation is concerned, is to usetriple Weber carbs, For mostpur’poses on the 2000 engine, 40DCOE Webers work out very nicely.We can consider the use of Webercarbs right from square one but theywill come into their own more on anengine which has seen mods in otherquarters. For an all out competitionengine, 42 DCOE Webers will give asmall gain in power over the 40’ssomething between 2-3 b.h.p. beinggained by their use. As soon as westart making vast improvements onthe inlet side of things on the Triumph6’s, the inadequacy of the exhaustsystem becomes apparent. To get thefull benefit of a good set of triple carbsone should give serious thought to achange in exhaust manifolds. This willallow the full potential of the carbs tobe gained in the middle and upper rev.ranges. For road use all tile pipes ofa high efficiency exhaust manifold canbe fed into one silencer so long as ithas a reasonable bore. Better resultshowever, can be gained by using twotail pipes, each one connected tothree of the cylinders. There is little tobe gained by messing about with pipelengths on an exhaust system whichhas to have silencers fitted. Oneshould concentrate on reducing back-pressure by selecting a pair of good

straig ht- through silencers. On theother hand if the car is to see usewhere open exhaust can be used,then our exhaust pipe length can bemade to work for us. The hotter thecam the more critical the exhaust pipelength becomes. With a really hairycam, the correct exhaust length canresult in 10 b.h.p. gain at the wheelson a 2-litre car and that amount ofpower is not to be sniffed at. Unlessone has facilities to make up mani-folds complete, there is little one cando about the primary lengths of theexhaust system. So long as the pri-mary pipes are of a reasonable length,which is the case for most exhaustmanifolds sold by tuning firms, we canadvantageously juggle the secondaryor tail pipe length. This length is go-ing to depend on the cam used andthe length of the primary pipes, if aproprietary exhaust system is used.Adjustment of the pipe length, foreach group of three cylinders, shouldbe done on a dynomometer. As arough guide, you will find that thelength will be around the 30" mark I6" for each of the two tail pipes. Thediameter of the tail pipes used, needsto be in the order of I 7/8" -2 “. If youcan have an exhaust system speciallymade up for use with a full race cam,then the following sizes should beused: 1 3/8” bore primary pipe x 36'long into 2" dia. tail pipe 24' long num-bers 1, 2 and 3 primary pipes feedinginto one tail pipe and numbers 4, 5and 6 feeding into the other. The tailpipe length may need to be finally seton a dynomometer because of thevarious types of full race cams avail-able but in the main, will not needchanging by more than about 3'. Itshould be pointed out that even a 3'change in tail pipe length can makeseveral horsepower difference.

105

Fuel injection

We have talked of carburationchanges and exhaust manifolds andthe time has come to took at fuel in-jection. We are likely to come acrosstwo types of fuel injection on Triumphcars. The Lucas type fitted as stan-dard to the T.R.5 and 6 and the 2,500P.l. and the Tecalemit/Jackson-sys-tem which is, of course, not a stan-dard fitment. Both systems rely on aprofiled cam to give the correct fuelmetering throughout the rev. range. itthe engine characteristics arechanged, the profile of the fuel camwill have to be altered to suit. Usuallythe largest single influencing factor isthe type of camshaft fitted. As pointedout before, you can buy a camshaftwhich is designed to go with the stan-dard fuel cam on those engines hav-ing Lucas fuel injection. When fittingsuch a cam to the Lucas injected en-gine, the overall mixture may have tobe adjusted but the standard fuel camcan remain. Unless you happen to bean expert on either type of fuelinjection,the setting up of injectors isbest left to an expert. This setting upshould be done on a dynomometer inconjunction with a mixture analyser.With this sort of equipment, one candetermine and try a variety of fuel camprofiles to enable the fuel injection ona tuned engine to show up at its best.It the car you are going to tune hasnot already got fuel injection and youdecide to have it fitted, then in all prob-ability you will go for the Tecalemit/Jackson equipment. If this is the case,then S.A.H. have a variety of fuelcams to suit different stages of tunefor the six cylinder Triumphs. Thisbeing the case, one should not expe-rience undue problems with the T.J.

system as far as metering accuracygoes. Even if a fuel cam is selectedwhich is near enough right for the jobin hand one should still set up the sys-tem on a dynomometer for the bestresults.

To make sure you are not put offinjectors by their seemingly complexnature, let us look at the advantagesof their use. First off you get morepower. Just how much more reallydepends on the state of tune of theengine. It the engine is in a relativelymild state of tune, we may only gain3-5 b.h.p. over a really good set ofcarbs like Webers, for instance. Onthe other hand if the engine is fullytuned, the gain over carbs can be 8-10 b.h.p. Some mods to the standardbarrels or intakes can raise this evenfurther. The power gain is not the onlyadvantage of injection. We can alsoget better flexibility and a slight wid-ening of the power curve which willenhance the driving characteristics ofthe car. With either the T.J. or theLucas injectors, one has definitely gotthe edge on carbs but either of thesesystems can, with good effect, bemodified to give even better results.

Before delving into the ins and outsof fuel injection systems, a couple ofpoints should be considered. TheLucas system is built for road use andas such any mods for racing will in allprobability have to be carried out bythe owner or some tuning firm willingto tackle the job. The T.J. system ison the other hand built for both roadand racing, the racing injector beingof a slightly different form. Since T.J.are very much connected with com-petition, one can get a fuel cam spe-cially made up to suit any engine inany state of tune which is using theirinjectors.

106

This now only leaves us with a fuelcam problem for the Lucas injectors.If you do not fancy trying to developyour own fuel cam then any tuningdone to the engine will have to becompatible with the standard fuelcam. Even if this is done one will haveto make overall adjustments to themixture. If the overall breathing abil-ity of the engine has been improved,the mixture will in all probability needto be made richer by altering the ba-sic slope of the fuel cam. This isachieved by loosening the two screws‘A’ in Fig. 48 and moving the contactpoint of the roller on the cam awayhum the plunger. A small amount ofmovement gives a relatively largechange in mixture so do not be toorash, only make adjustments a fewthou. at a time. Moving the fuel camchanges the mixture at full throttleconditions and part throttle. If the part

throttle conditions are still found to beout, adjustments can be made by al-tering the screw denoted by ‘C’ in Fig.48. Undoing the screw will richen themixture, and tightening it will give aweaker mixture. We may also find acondition at full throttle and high revs.where the shuttle which moves backand forth between the two stops doesnot displace sufficient fuel, causing aweak mixture. If this situation occurs,and it is not likely, except on the mosthighly tuned engines, the remedy issimple. Both the fixed and movingstops are shortened by removingmetal from their plain ends. We can-not, however, continue to apply thismethod ad lib since too much short-ening will cause the shuttle to closeoff the fuel ports in its sleeve and de-feat the object of the exercise. Againany adjustments should be made byremoving metal

107

108

at a few thou. at a time.If one is using injectors without air

filters one can obtain a useful in-crease in power by fitting ram pipesto the injector intakes. These itemswill have to be specially made upsince there are no proprietary onesavailable. The form these ram pipesshould take are as shown in Fig. 49.These will give a power increasearound the 5-6 b.h.p. mark, so theyrepresent a fairly worthwhile modifi-cation. Of course, if we really want toget fussy over things we can get a bitmore power by completely remakingthe injector bodies and at the sametime, do away with the conventionalbutterfly. Fig. 50 gives a suggestedlayout of an injector body suitable foruse with the downdraughted headshown in Fig. 40. This injector bodywith the downdraughted head and asuitably hairy cam could conceivablygive the power output required of ourhypothetical 2-litre racing engine.

To round this off a little somethingshould be said about carburation andmanifolding for the four cylinder en-gines. The standard carburation forthe TR4 and 4A is either a pair of 1-3/4" S.U.s or Stromberg C.D.s. Thestandard carbs can be used on en-gines tuned to give 135-140 b.h.p. butthey are on the limit. The fitting of big-ger carbs of the S.U. or Strombergvariety is not the complete answer.Since we have an engine with fourinlet ports we may as well make fulluse of them. As such the fitting of a

pair of DCOE 45 Weber carbs is tobe highly recommended. On an en-gine which is already giving 135-140b.h.p. they will add to this another 10b.h.p. The standard exhaust manifolddoes tend to make power reductionsover about 4,500 which are of size-able proportions. The fitting of an ex-tractor manifold such as those itemssupplied by V. W. Derrington or S.A.H.can result in about 7-8 b.h.p. gain. TheTR4A exhaust system has two silenc-ers fitted, the exhaust pipe splittinginto two separate pipes about half waydown the car. If possible, this shouldbe replaced by a single pipe systemusing one large straightthrough si-lencer. An exhaust pipe diameter ofapproximately 2" should be used fromthe junction at the manifold rightthrough to the silencer and on out tothe tail pipe. If open exhausts are tobe used and the engine is equippedwith a full race cam, Webers, etc., atail pipe of about 40-45" is required,the length being measured from theend of the extractor manifold to theend of the tail pipe. The diameter ofthe tail pipe is best around 2-1/4"which in most cases will mean a stepup from the manifold size. This canbe done by sleeving the manifold pipeup to accept the tail pipe. To preventthings dropping apart the sleevesshould be welded to the manifold andthe tail pipe clamped to the sleeves.If you weld the whole lot together youare likely to experience great difficultyremoving the manifold from the car.

109

WE have up to this point discussedvarious ways and means of modify-ing the engines, but very little hasbeen said as to the power increasegiven by any one or a combination ofmodifications. The power outputsquoted by the factory are rarely if ever,shown in practice. In most cases thefactory quote figures gained underconditions which could never exist inthe car, the net result of which is apower unit which is often about 10%down on the factory quoted figures.Consequently we often find that acertain amount of modifying is nec-essary before we can achieve the fac-tory quoted power output. The amountbelow the quoted power output var-ies from one make of car to another.

chapter 16

ASSESSING THE RESULTS

TR4 &4A 2000 c.c. 98 b.h.p. “ “ 2138 c.c. 102 b.h.p.1600 Vitesse 1596 c.c. 70 b.h.p.2000 Mk, 1 1998 c.c. 100 b.h.p.G.T.6 Mk. 1 1998 c.c. 100 b.h.p.Triumph 2000 Mk. 1 1998 c.c. 100 b.h.p.2000 Vitesse Mk. 1( 1998 C.c. 105 b.h.p.G.T.6 , Mk. 11 1998 C.c. 105 b.h.p.Triumph 2000 Mk. 11 1998 c.c. 105 b.h.p.2.5 P.1, saloon 2498 c.c. 135 b.h.p.TR5 Et 6 2498 c.c. 135 b.h.p.

It would appear that in the main, Tri-umph figures are within a few per centof the quoted figures, indeed, if any-thing, the early 2000 engine was un-der quoted which is quite unusual. Toavoid further beating about the bush,let us go to some power output fig-ures for completely bog standard en-gines which have been carefully builtup and then set up whilst on thedynomometer.

Starting at the top of the list andworking downwards, the power out-put at a number of successive stageswill be given in the order in which theyshould be done, if tuning is done instages.

Starting with the TR4 and 4A, thefirst modification should be a re-

110

worked head. This will put the powerup from 98 b.h.p. to 108 b.h.p. Theaddition of an extractor exhaust mani-fold will raise that to 114 b.h.p., stillwith silencer. A half-race cam willraise this still further to about 120b.h.p. and a fullrace one, to about 124b.h.p. With a fullrace cam, the silencerhas quite a profound effect and theremoval of the silencer plus the sub-stitution of the correct length of pipewill put the power up by another 8b.h.p., bringing it to 132 b.h.p. At thispoint the standard carbs are definitelychoking the engine, and the fitting of45 DCOE Webers is called for. TheWebers at this stage will put up thepower to 142 b.h.p. These figures arefor the 2-litre engine. By using the 2.2litre engine with the largest pistonavailable (87 m/m), the power outputcan be raised by a further 9-10 b.h.p.,bringing it to a little over 150 b.h.p.

With the 1600 Vitesse engine fittedwith the Solex carbs one should con-sider the changing of the carbs as oneof the first modifications. A modifiedhead fitted to a 1600 engine withSolex carbs will only give about 4-5b.h.p. increase. On the other hand amodded head fitted to a 1600 enginewhich is using twin Strombergs willgive around 8-9 b.h.p. increase. Thefitting of triple S.U.s will give about 10b.h.p. increase on top of the amountgiven by a Stage 1 head, bringing thepower up to 88-90 b.h.p. At this stagea good exhaust system becomes es-sential if any further power increaseis required and its fitment will, underideal conditions, push up the powerto about 95 b.h.p. Fitting a half-racecam at this stage will bring the powerto about 100 b.h.p. The replacement

of a Stage 1 head by a Stage 11 headwill show around the 105 b.h.p. markas a result. If we go really mad and fitall the hottest goodies going, such astriple Webers, Stage 11 head, full racecam, etc., we should expect the powerto be in the- region of 130 b.h.p. TheMk. 1 2-litre engines will show thesame basic increases as the 1600engine, but because of its greatercapacity, the power will be up by1520% at each stage. On 2-litre en-gines, using fuel injection instead ofcarbs, the power can be brought upto 160 b.h.p. plus, when suitablecams, heads and exhaust are used,even without resorting to super headsand very sophisticated injector bod-ies, etc., etc. If we do go to such ex-otic means for gaining power than 190b.h.p. plus should be possible.

With the 2.5 litre engine, the firststep is to modify the head, This willresult in a gain of about 8 b.h.p. Sinceall the 2.5 litre engines with the ex-ception of the TR250 have fuel injec-tion, the fitting of a good extractormanifold should be considered next.For the TR250 some improvementsin carburation are needed before go-ing to the exhaust side of things. Fromthis point on, any further increase on2.5 litre engines should be done bychanging the cam. By selecting a camsuitable for use with fuel injection, thepower output can be raised to 165-170 b.h.p. and still retain reasonableroad going characteristics. A full racecam, open exhausts of tuned lengthand other competition items can giveup to 180 b.h.p., but by this stage thetractability in the lower rev. range hascompletely gone.

111

THE TR4 clutch is of the spring type,and as such is capable of handlingup to 140 b.h.p. Beyond this one islikely to experience a fairly short clutchlife before clutch slip starts to set in.The TR4A clutch is capable of takingmore power than the early TR4 clutch,and is of the more modern diaphragmtype. The TR4A clutch can be usedin the TR4 but it means swopping afew more components other than theclutch itself. The securing holes in theflywheel are different for the springclutch as compared to the diaphragmunit. This can be remedied either byredrilling the TR4 flywheel to acceptthe diaphragm clutch or purchasinga TR4A flywheel which will fit directlyto the crankshaft of the earlier engine.Incidentally, the TR4 flywheel is a lotlighter than the 4A flywheel in stan-dard form. After lightening, both fly-wheels will weigh the same. Whenchanging from the earlier clutch to thelater one, the appropriate clutch plate,thrust bearing and thrust bearing car-rier sleeve must be used, all theseparts being as fitted to the TR4A.Since the diaphragm clutch can holdout against 150 b.h.p. we should not

experience too much trouble in thisquarter

The 1600 Vitesse spring clutch canbe treated in a similar manner-TR4to 4A swop. We can use the relevantparts from the 2-litre Vitesse to con-vert to a diaphragm clutch. The stan-dard spring clutch on the 1600 is allright for power outputs up to 105-110b.h.p. or so. After this, the use of thediaphragm clutch is to be advised.The 2-litre Vitesse and G.T.6 clutchesappear to be quite capable of trans-mitting 165 b.h.p. plus, so little atten-tion is required in this department.With a highly tuned Triumph 2000 ora 2000 with the 2.5 litre engine in it,some trouble with the clutch mayarise. This can be easily cured byusing the 2.5 P.I. clutch as it is some20% stronger and should suffice toabout 180 b.h.p.

Ratios

Gearbox ratios can be all importanton a car using a tuned engine. Sinceit would appear that very little is avail-able in the way of special gears forany of the Triumph cars,

chapter 17

TRANSMISSIONS

112

it is a good job that the standard ra-tios are pretty close. For instance the2-litre Vitesses and G.T.6’s have thefollowing ratios: 1st 2.65/1, 2nd1.78/1, 3rd 1.25/1, top 1 /1 O.D. top0.8/1. These, by road going standardsare pretty close. For racing one coulddo with ratios a little closer but thestandard ones do come quite closeto the mark. The early 1600 Vitessehas a lower first gear than the laterones at 2.93/1 instead of 2.65/1. Itwould appear to be a little awkwardto adapt the later gears into the ear-lier box so the easiest route is to usethe later box complete. The cost, timeand trouble of converting the earlierbox is just not worth it since practi-cally all the internals have to be re-placed and also some machining isrequired here and there. With the Tri-umph 2000 and 2.5 P.I., we can getslightly closer gearbox ratios by us-ing the TR4, 5 or 6 components.

The saloon ratios are: 1st 3.3/1, 2nd2.1/1, 3rd 1.386/1, top 1/1, whereasthe TR ratios are 1st 3.139/1, 2nd2.01/1, 3rd 1.325/1 and top 1 /1. Onecan either swop the gearbox andtailshaft assembly complete as a unitor swop the TR gears into the 2000or 2.5 P.I. box. If just the gears areswopped over, then one should retainthe original 2000 or 2.5 P.I. gearboxinput shaft as the spline on these dif-fer to the TR ones. If a complete TRgearbox is being installed, the strip-ping of the gearbox to fit the salooninput shaft can be avoided by usingthe TR clutch plate since the spliningin this will obviously match the TR boxinput shaft. If this is done then a checkshould be made to see that the inputspigot bearing is the right size. Also ifany difficulty is experienced throughmisalignment of bolt holes in the bellhousing (which is in one piece withthe gearbox on 2000s, 2.5 P.Is and

TRs) the back plate on the engineshould be swopped for the one rel-evant to the gearbox.

Although the TR ratios are not asclose -.s those found in the 2-litreVitesse and G.T.6, they are wellsupplemented by overdrives. Thesaloons have an overdrive effectiveon the top two gears and the TRs onthe top three. For most purposes then,we will have an adequate selection ofgears. Overdrives, however, tend tobe a little unreliable for racing andsome benefit may be gained by us-ing the Vitesse or G.T.6 box in the bigsaloons or the TR sports cars. Thiswill give far closer ratios without re-sorting to the use of overdrives. Todo this one will need to use the G.T.6or Vitesse gearbox, tailshaft, gearchange extension, bell housing andclutch release mechanism. On the2000 and 2.5 saloons the clutch to useis the 2.5 P.I. one. The difference inheight from the clutch face to thespring tips between this clutch and theG.T.6 unit is insufficient to cause anyundue bother. The same also goesfor the TRs but here we should checkthe spigot bearing clearance for a run-ning fit. The tailshaft of the G.T.6/Vitesse box is shorter than that of bigsaloons and the TRs. The prop shaftwill need to be lengthened to compen-sate.

Final drive

Having juggled the gearbox or gear-box ratios to suit our requirements weshould select a compatible final driveratio, bearing in mind the sort of us-age the vehicle is to be put to. Start-ing again with the TR4, 5 and 6, wefind that standard final drive ratios areavailable at 3.7/1 and 4.1/1. For finaldrive

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

ratios other than these we can go toS.A.H. and they can supply ratios at3.45/1, 4.3/1, 4.55/1 and 4.875/1.Since the 2000 saloon and 2.5 P.I. usebasically the same final drive unit, allthese alternative ratios will apply tothese cars as well as the TR sportscars. When selecting a final drive forthe TR sports cars or the big saloons,we must carefully. consider what thefinal application of the car is to be. Ifa high cruising speed is required with-out excessive engine revs then a ra-tio higher than standard should beselected. If maximum top speed isrequired, one should stick to the stan-dard ratio nine times out of ten. Theonly occasions which warrant the useof a higher final drive for all out topspeed is when the engine has beenmade to produce a good deal morepower without any appreciable in-crease in the r.p.m. at which it pro-duces this power. Coupled to this wemust bear in mind that both the sa-loons and sports cars are fitted withoverdrives. This means that for topspeed, the overdrive ratio is plentyhigh enough. If, by some chance, youhave a car without an overdrive, thenif the engine has had considerablemodifications at the top end and acam designed for torque, then it canconceivably benefit on top speed byusing a higher final drive. The onlydrawback to this is that it will reducethe acceleration. The best solution toretain acceleration and get top speedis to fit the overdrive unit if it is notalready fitted. By dropping the finaldrive ratio to the next lowest, the re-duction in top speed is only marginalbut the acceleration is better. For thebest acceleration for the saloons weshould go for the lowest final driveratio or the one above the lowest, e.g.4.875 or 4.55. With the 2000, the

4.875 will probably be found to be thebest. The 2.5 P.I. should be just righton the 4.55. When using these lowfinal drive ratios it is advisable to usethe closer ratios of the TR sports carsin the saloon. If this is not done, onecan end up with too much torque atthe rear wheels in bottom gear. Ex-cessive rear wheel torque just mani-fests itself in the form of excessivewheelspin which is not really the bestmethod of getting off the line. If rac-ing tyres are being used instead ofroad tyres, excessive wheelspin is farless likely to occur, due to the bettergrip of the racing boots. If all the rel-evant factors are taken into account,then the selection of a final drive ratiocan become a little complex. Probablythe easiest way to ascertain which fi-nal drive ratio will do the job is to lookat the graph, relating engine speedsto road speeds in various gears, Fig.51. This should give us a good insightas to what is going on. Other factorswhich will contribute to our selectionof a final drive ratio, for maximumacceleration, are (a) the weight of thecar, (b) the revs at which peak poweroccurs, usually influenced mostly bythe type of cam fitted, (c) the spacingof the gearbox ratios, and (d) theamount of grip we have at the backwheels. We can apply some basiclogic which will assist us to select thefinal drive, although it will be by nomeans foolproof. As a starting pointwe can assume that if no other con-ditions exist which are detrimental toaccelerationsuch as too muchwheelspin - then the lowest final driveratio will give us the best acceleration.So at this point we arbitrarily selectthe lowest ratio available. However,much we may surmise, other factorsdo bring

132

to bear a considerable amount of in-fluence, so we will not take these intoaccount.

Firstly, if road lyres are being used,we have less grip available than ispossible by using racing lyres. Theextra torque at the wheels is there-fore being wasted by lack of sufficientgrip and this will make bottom gearless useful than it possibly could be.The answer is to go up one, maybetwo ratios from the lowest. Againstthis must be weighed the effects of acloser ratio box. If ratios as close asthose fitted in the Vitesse or G.T.6 areused, then we must consider goingdown on final drive ratio to compen-sate for the higher bottom gear. Sincethe Vitesse/G.T.6 bottom gear isnearly as high as a 2000 or 2.5 P. I.second gear, one would anticipategoing down one or possibly two ra-tios from the ratio which had last beenarrived at due to other considerations.

If the car is lightened considerably,then we can again come to the stagewhere it is possible to have the rearend gears at too low a ratio. With thebig Triumph saloons and the TRsports cars we can say approximatelythat each 10-15% reduction in weightwill call for a final drive ratio one ratiohigher than the lowest available. Wecannot make this too much of a hardand fast rule because it does dependwhere the weight has been removed.If the reduction in weight means thatboth front and rear wheels becomeless loaded by an even amount, thenthe aforementioned approximationwill hold fairly true. If the lightening,instead of being 50/50 front and rear,is 70/30 front and rear, the effect onthe final drive ratio will be less so thismust be taken into account.

The last point to be considered is

the effect of the camshaft, since thishas a distinct bearing on the width ofthe power band. A cam up to abouthalf race spec. can usually run oneratio higher than a full race cam.Strictly speaking it is better to say thatthe full race cam should be run to-gether with a lower final drive than ahalf race cam, primarily because itenables one to make better use ofimproved top end power. Superim-posed on top of all the aforemen-tioned considerations is the fact thatthe car must have sufficient top speedwith the final drive ratio selected. Ifthe car is to be used for competition,the best plan is to find out from othercompetitors using a car with a similarpower to weight as your own, whatspeeds they attain. You then selectyour final drive to give you a top speedsomewhere in the region of 10-15%in excess of this. The graphs given inthis chapter should help in your choiceof final drive ratio. The technique touse is as follows: first establish ther.p.m. at which peak power occurs.Multiply the peak power r.p.m. by 1.1, i.e. increase it by 10%. Using this asdatum r.p.m., find the various speedsgiven by various final drive ratios rel-evant to your car on the graphs given.Select the ratio that most closely givesyou the top speed required. If you findyour selected speed falls half waybetween two ratios, the best bet is tostart off with the highest one. Select-ing a final drive for the road is lessdifficult than for track purposes. Youneed only decide on what top speedwill suffice, assuming the engine hasenough power to reach it, then lookthrough the graphs until you find theratio which will give you that speed atan r.p.m. 10-15% over peak powerr.p.m. If you are gearing for all out top

133

speed, do not think that the highestfinal drive will necessarily give youthis. The final drive ratio for top speedmust be equated to engine poweroutput. The higher the final drive, thehigher the power, or to be more pre-cise, the torque output of the engineto pull it. If the engine is not puttingout the power required, overgearingwill serve only to reduce the topspeed. If you are gearing for topspeed, then you need to know exactlyhow much power is required to reacha given speed. If your engine is de-veloping the power required to reachyour target speed, then you select afinal drive which will allow the peakpower r.p.m. to coincide with the topspeed. Practice shows in most casesthat unless engine torque has in-creased appreciably then the highesttop speed is usually achieved with thestandard final drive or one either sideof it.

Having dug into some basic theoryon final drives, I think it best that weshould come back to reality and dis-cuss just what is available for theG.T.6 and Vitesse in the way of rearend gears. The standard ratios for the

G.T.6 and Vitesse are 3.89/1 or 3.27/1. To augment these two, S.A.H. cansupply ratios at 4.11 and 4.55. Formost purposes, this range of finaldrives is adequate and you should findone of the four suits.

Having got the engine to put out arespectable amount of power it is es-sential that we get it down to the road.To help power transmission to theToad a limited slip differential is a re-ally useful item to have. Should therebe appreciably less grip at one driv-ing wheel than the other, the powerwill get transmitted through to thewheel with the grip. The result of fit-ting such a device is a better take offfrom rest, due to less wheelspin. Italso allows the throttle to be appliedharder and sooner when coming outof bends, especially tight ones. Forany form of competition work, a lim-ited slip differential must be consid-ered a vital piece of equipment. Lim-ited slip differentials for the cars inquestion can be obtained from S.A.H.who, as you have probably guessedby now are one of the biggest suppli-ers of Triumph tuning equipment.

134

135

136

137

THE pleasure and ease of driving anyparticular car can be made or marredby its roadholding or braking qualities.Should either of these departmentsbe seriously deficient, then it is pos-sible to have a downright dangerouscar. All the Triumph cars with whichwe are dealing have roadholding andbraking compatible with the poweroutput of engines in standard or mildlymodified form. The braking depart-ment is usually up to a far higher levelthan the roadholding, and in conse-quence quite an amount of extra per-formance can be handled by thebrakes before any deficiencies startto make themselves felt. If you findthat your particular car seems to lackthe roadholding or braking power youthink it should have, do not immedi-ately jump to the conclusion that itneeds to be modified to effect a cure.Brakes and suspension are prone towear just as any other working com-ponents. Any wear in the suspension,steering and brakes can bring abouta big reduction in the handling quali-ties, so before any modifications areconsidered, make sure that wear is

not the culprit for below par perfor-mance.

If the car is to be used for a specificpurpose and you definitely want tomodify the suspension or brakes, thenany worn parts can be replaced dur-ing the modification process. As such,we will run through the procedure formodifications to each car which willeither improve roadholding or brak-ing make the car handle in the fash-ion you want it to.

TR4

The first move on suspension modi-fications for the TR4 is to fit an antirollbar, which can be acquired from V.W. Derrington or S.A. H. This gives amarked reduction in roll during cor-nering, it increases the maximum cor-nering ability and on top of this, givesthe driver a greater confidence as thecar feels more sure footed.

The next step from here is to fitfirmer shock absorbers.

A good combination to use wouldbe the Spax adjustable on the frontwith the Armstrong Firmaride on theback, but of course this is only

chapter 18

SUSPENSIONS AND BRAKES

138

personal preference and you mayhave your own idea as to what shouldbe used. Armstrongs do, apart fromthe shock absorber listed above,make a special range which are avail-able only through S.A.H. Theseshocks are available as adjustable orfixed for the front and fixed for therear, which is as listed above.

Wider wheels can improve theroadholding but for road use with roadtyres we should not overdo things. Forthe front 5 1/2.-6J wheels will workout just right. On the rear 6-6 1/2 areneeded. Although alloy wheels suchas ‘Minilite’ are the best, they are quiteexpensive. As an alternative, one canuse widened steel wheels whichworks out far cheaper. A firm whichcaters for widened steel wheels andproduces a very fine finished productis Weller Racing Wheels, Edenbridge,Kent.

If the suspension is to be modifiedfor racing or rallying, we will need togo a little further. To start with, stiffersprings are needed and maybe somealterations to the ride height. Firstlyon the TR4 two types of front springsare fitted. One is short and the otheris long. The short ones were used onthe earlier TR4 which has a packingblock above the spring (see Fig. 52).The later ones did not have this pack-ing block and the distance lost wasmade up for by a longer spring. Theshort spring (free length of 9.75") hasa rate of 310 lb. per inch. The longspring (free length of 11.1 “) has a rateof 312 lb. per inch. A competition frontspring which is available through

S.A.H. has a rate of 380 lb. per inchand a free length of 9.2" which meansit is suitable as a straight swop on theearlier TR4. To use the competitionsprings on the later models we haveto reintroduce the aluminium packingpiece. If the competition springs areused, additional lowering can beachieved by machining the aluminiumpacking piece. These can be ma-chined top and bottom to achieve thedesired ride height (see Fig. 53). Theamount to be taken off the blocks isnot in direct proportion to the amountof lowering. The ratio between metalremoved from the blocks to thechange in ride height is about 5/8:1i.e. 5/8" off the blocks will lower theride height by about 1 “. When refit-ting the blocks do not refit the top rub-ber packing piece. It the ride heightneeds to be increased as would bethe case for rallying, then this can besimply accomplished. On the earlymodels, with the packing piece, fit thelater long spring. On the later mod-els, with the long spring, fit the pack-ing piece. In each case this will raisethe ride height of the front by about1 3/4 - 2” If this is too much, then thepacking pieces can be machined tomake the necessary adjustments. Ifthe S.A.H, competition spring is usedwhich is 9.2" long, shorter than eitherstandard spring, then the ride heightmust be adjusted by fitting an addi-tional packing pie - That is, two pack-ing pieces will be needed at the topof each spring , the standard one plusone to make up for the shorter lengthof spring.

Front RearArmstrong Adjustaride - - “ Firmaride - R-7999/-DAS9Koni Special D 80-1005 80-1108Spax Adjustable S164/209 -

139

140

Again, if the ride height is excessive,adjustments can be made by machin-ing one of the packing pieces.

The camber angle of the frontwheels may, under certain circum-stances, be found to be excessive aswould be the case if either the rideheight is increased or if the car is tobe used with wide racing tyres. Thestandard camber angle is 20 positivealthough this could be as much as 3-3 .50 if the ride height has been in-creased. If the car has been lowered,the camber angle will probably bedown to 1 -1 .50 positive. If the rideheight has been raised, for rallying,then the camber angle should be re-duced t o 0.50 - 10 plus when laden.Laden weight is equivalent to two pas-sengers 150 lb. each. If the car hasbeen lowered for racing and is usingwide racing tyres, then the camberangle should be set at 00 - 0.50 nega-

tive. To reduce the positive camberyou will need to make up new pivotplates for the bottom wishbone of thesuspension. Fig. 54 shows exactlywhich plates need to be remade. Foreach degree of positive camber re-duction required, move the pivot bolthole in the plate 0.170" outwards.

Early TR4’s had a 00 caster anglewhilst later ones have a 30 casterangle. You can tell which is which bythe top wishbone. If it is a onepieceitem made up of sheet steel in a rect-angular box section form with the topking pin or steering knuckle joint stuckon its outer edge, then the car has 00

caster. On the other hand if the topwishbone is a two piece affair with thetop king pin or steering knuckleclamped between the outer ends thenthe car has 30 of caster. The highspeed

141

142

handling will be found to be better withthe 3' of steering caster. The earlymodels can be converted by fitting thelater parts. The parts needed are: (a)two new top wishbones and knuck-les, (b) tie rod lever i.e. the lever at-tached to the hubs to accept the steer-ing motion imparted by the tie rods,(c) new bottom king pin trunnion orlower trunnion bracket as it is some-times called.

Rear suspension

Having flogged our way through thefront suspension, we had better takea look at the rear suspension. The firstthing that you will find apparent if youlook at enough TR4’s is that somehave a large aluminium block be-tween the axle and spring, and some

have not. It is, in fact, the early oneswhich do not have the spacer. Theobject of the spacer on the later carswas to reduce the effect of roll steerand it is very advisable to incorporatethis spacer, especially if the front endhas been decambered. If this is notdone, the oversteer, when corneringhard, may prove excessive. To con-vert the early rear suspension to thelater one, you need to acquire the laterrecambered springs (part no. 209964)together with the spacer blocks andlarger U-bolts. The only drawback tousing the spacers is that with a fairlyhighly tuned engine, axle tramp islikely to occur. If the stronger rearspring supplied by S.A.H. is used,then the possibility of axle tramp iseliminated. The S.A.H. spring must beused in conjunction with the spacing

143

blocks or the ride height will be about3.50 too high. For rallying the rear endcan be made higher by shortening thespacing blocks although there is alimit to how much the standard blockscan be shortened due to them havingan oval hole in the middle. Since thereis nothing very complex in the natureof the blocks, it is a straightforwardjob to make some shorter ones thatwill give the required increase in rid.-height. Lowering is obviously the re-verse of raising and can be achievedby increasing the thickness or heightof the spacing block.

As far as braking goes, we find thatthe standard braking can handle quitea bit more go. For competition pur-poses, a brake booster plus competi-tion linings will give the performancenecessary.

TR4A

All that has been said about the latertype TR4 front suspension applies tothe TR4A with a few exceptions.

Firstly the standard camber angleis between ‘1/20 plus-1/20 minus, andif the car is lowered it will end uparound 10 negative which is just aboutright for a circuit racing set-up usingthe stiffer front springs and racingtyres. If the car’s ride height has beenraised, the camber angle will be about10 positive and this should be reset to00. This can be done by adding pack-ing pieces where the bottom suspen-sion wishbone bolts to the chassis,see Fig. 55. The TR4A rear suspen-sion does, of course, differ vastly fromthe TR4 in as much as it is indepen-dent. S.A.H. offer two springs whichwill lower and stiffen the rear end. Oneis 1/2” lower and the other 1“ lower.In its lowered state the camber angleof the rear wheels is about 1 .5 - 20

which is just a little too much for usewith racing tyres, although it is all righton the road with road tyres.

To reduce the rear wheel camber itwill be necessary to move the holesin the fulcrum brackets which securethe suspension member to the chas-sis, see Fig. 56. The inner end of themember will have to be moved up andthe outer end down, to reduce thecamber. This means moving the holesof the inner bracket down and theholes of the outer bracket up. It de-pends on how much the car is low-ered as to whether both brackets willneed altering. If the excess camberis no more than 10 - you should aimfor 0- 0.50 negative with racing tyres-we need only alter the outer bracket.The holes in the bracket have to bemoved about 1/8" for each degree ofcamber change. The easiest way todo this is to fill in the original holeswith weld, file the weld flush with thesurrounding metal and redrill them inthe new position.

For increasing the ride height forrallying, one can obtain special adap-tors from S.A.H. but these can onlybe used with the standard springs.

As with the TR4, the braking depart-ment needs only minimal attention(assuming it is in perfect working or-der). If a servo is not already fitted,then it is advisable to fit one. This,together with harder linings, will do thetrick. The shock absorbers will be dif-ferent to the TR4 and the ArmstrongR-8686/1 - DAS10 will be found to besuitable for the TR4A rear end. Checkon rear roll bar.

TR5 and 6

The TR5 and 6 can be treated asfor the 4A. The only major differenceis that the TR6 is fitted with an antirollbar as standard. The brakes can

144

145

also be treated in the same manner.One thing that should be mentionedin connection with wheel rim widths,and this is applicable to all indepen-dently sprung TRs in connection withracing tyres. Rim widths should beabout 7" for the front and about 8" forthe rear. If we go too wide with wheelsand tyres the suspension set up be-comes hypercritical and as a resultboth handling and roadholding cansuffer.

2000 and 2.5 P.I. saloons

The front suspension of both thesecars needs very little doing to them.The first modification consideredshould be the fitment of an anti-rollbar. This will bring about a consider-able increase in roll stiffness butshould be ideally used in conjunctionwith a rear anti-roll bar. Incidentallyboth front and rear antiroll bars are

available from S.A.H. For further im-provements the ride should be stiff-ened up by fitting harder shocks suchas the Armstrong model AS 1514/5or Koni 82P-134a. For road work apair of 6 “ wide wheels on the frontend will increase the road holding fur-ther.

Lowering the front end can presenta problem in as much as there are noshorter springs readily available. Theonly way round this is to shorten theexisting springs. The standard springspecification is 129.5 lb. per inch, afree length of 13.23” with 6.5 workingcoils. If we cut off one working coil,i.e. shorten the spring by 2.03", theride height will be reduced by 1.78"and the spring rate will increase to 136lb. per inch. Of course if you do notwant to lower it as much as 1.75” thencut less off the spring. Over the rangewe are concerned with, the car is low-ered by approximately

146

7/8 of the amount the spring is short-ened by. If the car is lowered by 1 .75",which is suitable for track work but alittle too much for the road, the bumpstops should be made more progres-sive. This can be done by reshapingthem as shown in Fig. 57.

The camber and caster angles onthe front suspension are just right forhigh speed work and should not bealtered.

Should anyone decide to race oneof these saloons, I would suggest thefront wheel width with racing tyresshould be about 7-7.5". All the extraoffset on the wheels will need to beoutwards and a thin spacer, about 1/8”thick, may have to be used to stopracing tyres fouling the bottom springretainer on the suspension strut.

As mentioned before, the rear sus-pension should firstly have an antirollbar fitted in conjunction with the front.Stiffer shockers can be fitted to theback and the following shocks will givethe desired results. (Spax No. 164/216;Koni +80C-1 68, and Armstrongadjustaride A2933). The Koni unitneeds special brackets in order thatfitment can be carried out, so orderthese with the shocks. Stiffer rearsprings are available from S.A.H. tostiffen up the rear end which are justright for rally work where the nearoriginal ride height is retained. For usewhere the car needs to be lowered,we are slightly better off using thestandard rear springs shortened. Tolower the rear end 1-7/8" you will needto reduce the working number of coilsfrom 10.5 to 8.5, i.e. shorten thespring by 2.36". This means the ratioof spring shortening to lowering isagain about 7/8 to 1. By reducing thenumber of working coils to 8.5, thespring rate will go up from 260 lb. perinch to 320 lb. per inch.

When the car is lowered, the cam-ber angle on the back may be exces-sive. With road tyres 1-1.50 negativeis OK but on racing boots 1/2 - 3/40 isrequired. The same method is usedas on the rear suspension of the in-dependent TRs for reducing excessnegative camber. If racing tyres areto be used on the rear, then rim widthsaround 7.5 - 8" would seem appropri-ate. For road use 6 - 6.5" rim widthsshould be used.

Before winding up the sus-pension side of things on these cars(2000 and 2.5 P.I.) a little word ofwarning. For road use, if we are toavoid continual bottoming on thebump stops when carrying four pas-sengers, lowering should be limitedto about 1” front and rear. For racingwhen only one occupant is carried andthe roads encountered, as on a cir-cuit, are relatively smooth, the lower-ing can be carried out to a greaterdegree, up to say 1.75”.

Vitesse and G.T.6 Mk. I and II

Before delving into the “ins” and“outs” of the suspension modifica-tions, it should be pointed out that therear suspension on the Mk. II G.T.6and Vitesse differs quite appreciablyfrom the Mk. I versions.

The Mk. I version uses the swingaxle arrangement, which means asthe wheel moves up and down so thecamber angle of the wheel exhibits aproportional angular change, i.e. if theaxle swings through 20 the camberangle changes 20.

The Mk. II version uses a doublewishbone type of rear suspensionwhere the spring which is in the sameposition as the Mk. I version acts asthe top link. The end result of the sus-pension change is that the degree of

147

camber change with respect to sus-pension travel is far less on the Mk. IIcars than the Mk. I cars. Fig. 58 willshow clearly the difference betweenthe two types of suspension.

Since the general train of thoughthas got onto new suspensions, we willdiscuss the modifications to the Mk. Irear ends. The biggest drawback toswing axles is the fact that they tendto allow the wheels to tuck underwhen fast cornering is being indulgedin. This tucking under completelyspoils the handling of the car and it isone of the first things to give attentionto when modding the suspension.There are two ways in which this prob-lem can be overcome. Firstly one canfit the S.A.H. recambered rear springwhich sets the static negative cam-ber at 30-50 instead of the 10 to 00

found standard. This gives a vast im-provement in the high speed handlingqualities of the car and is fine whenroad tyres are being used. If racingtyres are going to be used, then 30-50

negative is far too much. The otheralternative is to use the Speedwellcamber compensator. When this isfitted it acts as a stiff but neverthe-less flexible bottom link and effectivelystops the wheels tucking under dur-ing hard cornering. If a camber com-pensator is used then the camberangle of the wheels is best left un-changed from the standard 10-00.

If lowering of the rear end iscontemplated, then the fitting of theS.A.H. recambered spring accom-plishes recambering of the backwheels plus a degree of lowering,about 1 -1.5”. If we are to lower therear end without getting too muchnegative camber then life gets a littlemore complex. We could, by packingthe spring up in the middle, lower therear end (this would achieve almost

the same thing as a recambered rearspring) but we should end up with toomuch negative on the back. Really theonly solution would appear to be tomove the whole axle assembly uprelative to the chassis. The easiestmethod to do this would be to removethe rubber bushes and cut off thesmall towers on the final drive frontmounting plate (see Fig. 59). A cor-responding change will have to bemade to the rear final drive mountingby moving the holes in the chassisupwards by the same amount as thefront of the final drive (see Fig. 60).All this effort should result in about1.25" of lowering. If a camber com-pensator is then used with this set-up, we have a suspension which isusable for track work or road usage.Remember that we must not haveexcessive negative camber for usewith racing tyres. The static ladennegative camber should be no morethan 10.

For track or high speed road use,stiffer rear shock absorbers should befitted. Any of the following type ofshockers can be fitted to the rear endwith good advantage; ArmstrongAdjustaride A.2612, Spax 164/211 orKoni 80C-1389.

For use on the road 5.5" or 6" wheelrim widths are best and radial tyresshould be used. Cross-ply tyres areprone to an early breakaway due tothe large camber angle changeswhich can occur. If the rear suspen-sion has been modified there will notbe anything like as much camberchange. Do not, under any circum-stances, use cross-ply tyres on theback and radials on the front-it turnsthe car into a mobile death trap. If youare going to use racing tyres, whichare definitely not

148

149

150

151

recommended unless the rear sus-pension is fully modified, rim width inthe order of 7.5-8" will be required.

The ultimate rear suspension modi-fication for the Mk. I G.T.6 and Vitesseis to convert it to the Mk. 11 spec. Thiscan be done by purchasing the wheelhub carrier assembly, drive shafts,rubber doughnuts and bottom wish-bones. A bracket needs to be weldedon to the chassis to accept the pivotpoint for the lower wishbone. If this isdone, the pivot point hole in thebracket needs to be in such a posi-tion to give 10 negative camber in thestatic laden condition.

This brings us very nicely on to theMk. 11 rear suspension. Unlike theearly suspension this does not sufferfrom the rear wheel tucking under, sono problems arise from this quarter.The first step which should be under-

taken to improve the handling is thefitting of harder shocks. (ArmstrongR62-4181 or Adjustaride A.22236,Spax 164/211).

To lower the rear end we can eitheruse a recambered spring or fit a pack-ing block under the spring at theclamping point. With the rear end low-ered by 1-1.5" you should find thenegative camber is just right at about10. If racing tyres are to be used, thenyou should attempt to get the 10 nega-tive as near as possible. If it is moreor less than this, the pivot point of thelower wishbone should be moved inor out to compensate. This will haveto be done by firstly elongating thehole to establish the correct position.Having done this, the excess part ofthe hole should be filled with weld thentidied up with a file. The under

152

steer or oversteer characteristics canbe influenced to a degree by adjust-ing the tie rods. There is no selling inparticular that will give the bestroadholding but it does allow the driverto set up the handling within limits tohis own requirements. By shorteningthe tie rod adjuster shorter, the han-dling will tend towards understeer andby lengthening the tie rod, the ten-dency will be towards oversteer. Byadjusting the tie rods we are alteringthe toe in on the back wheels. Therange over which adjustments can bemade for the purposes of setting upthe handling are from 2/32” to 0" toein.

For road use, wheel rim widths of5.5-6" are advisable while track usewill warrant wheels of about 8" fittedwith suitable racing tyres.

The first modification to the frontsuspension is the fitting of stiffershock absorbers. (Koni 8OH-1 388,Spax S164/210, ArmstrongAdjustaride SA 2697). This enhancesthe stability and sure footedness whenhigh speed cornering is indulged in.Going one step further, shorter frontsprings (available from S.A.H.) can be

fitted and these will reduce the rideheight by about 1 .5-2". The increasedstiffness of these springs togetherwith the reduction in centre of gravityheight brings about a useful reductionin roll during hard cornering. They alsobring about an increase in front wheelcamber of about 10, a degree moretowards negative that is.

The standard front and camberangle is about 2-2.50 positive in thestatic laden condition, i.e. carrying two150 lb. passengers. The shortenedspring will reduce this to 1 -1.50. Forroad use we can reset this to 00 byinserting packing pieces between thebottom wishbone pivot bracket andchassis (see Fig. 60). For circuit workthe ideal camber angle is 0.50-10

negative, this being right when the caris shod with racing tyres. Wheel rimwidths for the front for road work willbe the same as the rear at 5.5 to 6".For racing 7-71/2” will do the jobnicely.

As far as brakes go, if youhave a servo and harder linings theywill adequately perform the job ex-pected of them.

153

THE main subject to be dealt with inthis chapter is the use of lightweightbody components. The use offibreglass replacement parts canbring about a useful reduction inweight and hence increase the powerto weight ratio. In some instancesthere are glass components availablewhich make a quite staggering reduc-tion in weight.

Chris Williams (fibreglass compo-nents) is a specialist in fibreglassparts for Triumphs. One of his petprojects is a complete G.T.6 bodyshellin glass. This includes wings, doors,bonnet, boot, roof, undertray, bulk-head, etc., in fact all the originalpressed steel parts are remade infibreglass. The net result is a weightreduction of over 2.5 cwt. If you couplethis to a racing set-up, having only thebare necessities, the overall weightreduction is just about 4.5 cwt. Thisgives us a percentage weight reduc-tion of about 30% and that has thesame result as 30% more power asfar as acceleration is concerned.

Lightening

Although we cannot make such

chapter 19

BODYWORK MODIFICATIONS

large weight reductions on the otherTriumph models, the weight reduc-tions that are effected play a part inincreasing acceleration. To give anidea of how even a small weight re-duction can pay off, let us look at anexample. Let us say that we fit a glassfibre bonnet on a TR4 and in doingso, lose 30 lb. or thereabouts. The factthat the 30 lb. lost weight is up thefront end means that our weight dis-tribution changes, giving more bias tothe rear end. This, in conjunction withthe decrease in weight, means thatwe will theoretically reach 80 m.p.h.about 0.1 second quicker. This smalltime difference might not sound likemuch, but it does mean a distancedifference of something in the orderof 12 feet. To put it another way, if youraced two identical cars with the ex-ception that one had a glass fibre bon-net and the other one did not, the light-ened one would be about 12 feet infront of the other by the time theyreached 80 m.p.h.

To be more practical it would be agood idea to see just what is avail-able for the cars in question for light-ening purposes.

154

As mentioned before, Chris Will-iams does a complete G.T.6 bodyshelf in fibreglass. Apart from this hecan also supply bonnets or boots forthe TR4, 5, 6 and the Vitesse bonnetunit. S.A.H. do a very smart Le MansSpitfire type front end for the G.T.6.E.V.A. are also in the market forVitesse and TR glassfibre compo-nents. The Triumph 2000 and 2.5 P.I.are not catered for as such, but bothChris Williams and E.V.A. FibreglassProducts will undertake the manufac-ture of oneoff components if ap-proached.

The flaring of wheel arches oftenpresents problems unless you hap-pen to be an ace panel beater. If youdo not feel up to flaring your ownwheel arches, then quite frankly thebest bet is to get an expert to do thejob. The appearance of an otherwiseimmaculately prepared car can becompletely spoilt by badly flaredarches. Funnily enough, expert panelbeaters can make short work of flar-ing wheel arches, and the job doesnot come as expensive as it would atfirst seem.

For competition work the use of

perspex windows is a great weightsaver. You can save 30-35 lb. on aVitesse by replacing the windows withperspex. Most regulations of coursedemand that the windscreen is of thelaminated glass type so no changecan be made there.

If rallying is contemplated then theunderside of the car will need ad-equate protection. S.A.H. supply arange of sump guards and undershields for these cars. This piece ofequipment is very necessary if wewant to avoid leaving half the innardsof the car on some projecting rock.For rallying, all the petrol pipes, brakepipes and wiring should run inside thecar and not outside.

If your car is to be used for compe-tition, then remember that nine tenthsof the battle lies in the preparation ofthe car. Preparation does not neces-sarily mean large financial require-ments. In most cases it just meanscareful, thorough and meticulousworkmanship. This should apply tothe whole car, engine, transmission,brakes, suspension and bodywork.The end result of painstaking work willbe a very fast and reliable motor car.

155

156

157

158

159