SUPPLEMENT No.3

Contents Gen Sec's Ramblings 1 The Twin Cam Introduction:

M.G. Sales Promotion 1 Nuffield Organisation Press Information

2-3 Stand - up and be counted 3 B.M.C. Answer to Piston Problems 4 Group Regalia, Documents & Spares List 4

GEN. SECS Ramblings. What afortunate way to be able to start the 25th. Anniversary of Twin Cam production, by these pages allowing readers to take themselves back to 1958 and absorb the thinking at Abingdon when putting the car on the market by inclusion of the two Introductory papers and associated photographs issued by B.M.C.

The other main feature by Jeff Wicks should help to bring together the owners of the rarest MGA -the De-luxe. Finishing off with a series of B.M.C. Service Memorandum, that dealt with piston problems.

After 25 years we can claim more than a third of the 2111 production registered, and about a fifth of the cars still1 have active owners around the world known to the Group.

This year a special effort is being made to serve these enthusiasts by: extending our range of documents and spares; and with particular attention aimed a t the Club's Silverstone Festival week-end we hope to provide some- thing for all, if only a modest gamble on our Raf- fle.

To bring the facilities through the post just request the 25th. Anniversary Celebration form or make use of the rationalised Regalia, Docu- ments and Spares List on the back page.

THE TWIN CAM INTRODUCTION The two articles that follow were made available by the Nuffield organisation Cowley, Oxford in early July 1958 to the B M C dealers as part of the M G MGA Twin Cam introductory pack along with the four photographs listed a t the end of the second article

M.G. SALES PROMOTION. Dated 1st. July 1958 New Twin Overhead Camshaft Engine

for The Famous M.G.A. Introduction. Already a brilliant performer with its standard 1.5 litre 0.h.v. engine of 72 b.h.p. at 5,500 r.p.m., the M.G.A. is now to be offered with an optional twin overhead camshaft engine of 1589cc. developing 108 b.h.p. at 6,700 r.p.m. Even by M.G. standards this is something pretty big, especially as the new engine achieves this output without supercharging. Maximum re- commended engine speed is 7,000 r.p.m. but valve crash does not set in until 7,600.

Needless to say the car's performance with this new engine is unequalled by any other current model of similar capacity or price. Dun- lop disc brakes, front and rear, give the control- led stopping power commensurate with the im- proved performance.

The overall performance and behaviour of this car is so much better than anything else available even at a much higher price, that a wide demand is confidently expected. Potential purchasers are, however likely to be fairly tech- nical and for these the information on the follow- ing pages should prove helpful to the M.G.A. Salesman,

Design and Development. Power development by an engine is dependent on the amount of explosive mixture that can be fed into the cylinders above the descending pis- tons. Thus for maximum power the gases must sweep into and out of the cylinder bores with the very minimum of restriction. The design of the cylinder head that best achieved this is that which offers a hemispherical combustion chamber with inlet and exhaust valves directly over the piston.

It was with such thoughts in mind that MG engineers considered over three years ago, how they could boost the power of the existing four cylinder 1.5 litre engine now used so extensively throughout B.M.C. Although the original inten- tion was to adapt what is now known as the 'B' series engine, the modifications found neces- sary during development proved so extensive that today it is more true to describe the twin 0.h.c. engine as an entirely new unit since only certain features of the block resemble the cur- rent standard 'B' series production.

The cylinder head is of aluminium with cast in valve seat inserts. The combustion chamber is hemispherical and both inlet and exhaust ports are individual to each cylinder and so shaped and positioned as to give complete free- dom of passage to the gases. The twin overhead camshafts are chain driven and double valve springs are employed.

The couterbalanced crankshaft, connecting rods (with fully floating little ends) and pistons are all specially designed, as is the large capac- ity cast aluminium sump with cooling fins. Even the cooling circulation is different since the out- let of the centrifugal pump is coupled by exter- nal pipe direct to the rear of the cylinder head.

One of the first experimental versions of this new engine was used in the T.T. race at Dunrod in the Autumn of 1955. Persistant misfiring lead to a half distance withdrawal, but back home work on the engine continued. Two years later, a supercharged version, driven by Stirling Moss a t Utah achieved 246 m.p.h. Still development work continued and it is only now, when the M.G. engineers are fully satisfied with the engine, that it is being offered to the public.

It cannot be offered for installation in exist- ing M.G.A.s as the modifications required are sufficiently extensive to require the closest supervision and control by the factory.

M.G.A.s built a t the factory with the new engine will have Dunlop disc brakes on all four wheels. This has necessitated the use of new centre lock disc wheels which alone give the required clearance for the rather bulky disc brake machanism.

Data and Performance Comparison. Twin 0 H.C. Basic MGA

Capacity 1589cc 1489cc Bore & Stroke 2 96in x3 5in 2.875inx3.5in Compression Ratio 9 9:1 8 3 : l

Twin Cam Group Supplement SAFETY FAST, April 1983 15

MaxB H P 108 at 6700 rpm 72 at 5500rpm Max Torque 105Ibs ft 80Ibs ft

at 4500 rpm at 3800 rpm B M E P 163Ibs ft 133lhs ft

a t 4500 rpm at 3800rpm Maximum rpm 7000 6000 Maximum speed 120 mpht 103 8 mph" Acceleration through Gears 0 30mph 3 75 secs 5 0 secs 0 - 50 mph B 95 secs 10 8 secs 0 70mph 14 55secs 21 4secs 0 8Omph 18 Osecs 32 1 secs 0-98mph 24 55secs - 0 100mph 30 4secs 0 11Omph 37 7secs - Maximum Speed in Gears 1st 33 mph 26 mph 2nd 54 mph 42 mph 3rd 86 mph 68 mph Overall Fuel Consumption

23 28mpg 27 31 mpg tMGAroad test "Vide Motor Department- MGA Coupe PrototypeTest 7 8 57

Results With the compliments of the Nuffield Organisation Cowley Oxford

NUFFIELD ORGANISATION PRESS INFORMATION. Please do not release until the ANNOUNCE- MENT DATE 15th July 1958.

1. NEWS SHEET. TWO-MILES-A-MINUTE M.G. ANNOUNCED

M.G.A. with Twin Overhead Camshaft Engine and Disc Brakes.

One of the most exciting sports cars to have ap- peared in recent years is announced today by the Nuffield Organisation.

It is a special equipment version of the MGA known as the M.G.A. Twin Cam. Its features in- clude:

Twin OHC engine of 1589cc dehvering 97 BHP a t 5,000 rpm and 108BHP at 6700 rpm,

Dunlop disc brakes on all four wheels. Dunlop centre-lock disc wheels. Maximum speed 120mph. (approx). Acceleration in the order of

The engine capacity has been increased to take full advantage of the International Touring Car Classification.

Since its introduction in 1955 the M.G.A. has achieved an enviable reputation for stabil- ity, safety, and road worthiness and it has been apparent that considerably increased accelera- tion and maximum speed were possible without infringing upon the validity of Safety Fast.

The new twin OHC engine gives the car exhilerating acceleration and speed. The new disc brakes - on all four wheels - ensure that it will stop in a convincing and consistent manner.

Performance. Using 6500rpm as gear-change point best

use of the acceleration can be made The car will reach lOOmph from rest and

11Omph from rest in the order of 31 and 38 secs respectively

With the standard MGA rear axle ratio of 4 3 1 and with Dunlop Roadspeed 5 90 X l 5 tyres top speed at 7000rpm is 121mph Brakes. The brakes are the latest Dunlop disc type which are famous for their success in racing

Thev awe the Twin Cam stouuina nower in . ..~ ~~4 * - ~ Conversion. keeping with its acceleration and speed.

Due to extensive modifications to the -.- . wneeis. engine. chassis and body, it is impossible centre.lock disc wheels by Dunlop have also to convert a standard MGA to the specifi- been developed on the race track, 0 - lOOmph in 31 seconds. cation of the Twin Cam. Disc brakes will They retain the advantage of the knock-on 0 - llOmph in 38 seconds. not be made for the basic M.G.A.

Home list Price /ex wnrksi MRO extra nlim wire wheel and, because of their "dished shaoe ----. , - ~ - .- ----- , - - - - r---

fQn tax1 - f77n 2. BRIEF DETAILS. provide clearance for the brake assemblies - - - - - . - . Total price - open two seater, £1.26 17s

coupe £1.35 7s

No other car offers such performance at such a price

Available in open and coupe form the Twin Cam will be made initially in small numbers It will not replace the current M G A range which will continue unchanged

Similar in appearance to the M G A this high performance version is recognisable by its centre-lock disc wheels and name on the boot lid and scuttle air ducts

"Twin Cam" Inherits All M.G. Features. The exciting new M.G. M.G.A. Twin Cam

inherits all the traditional M.G. features of fine performance, good handling, precise steering, snap gear change and first class brakes.

And now, with its new and exceptional en- gine and braking power, the Twin Cam is the finest M.G. to come off the production lines at Abingdon. Engine.

The engine has been developed from the sturdy and reliable B.M.C. 'B' series unit which is used in the MGA and Magnette and many other B.M.C. models.

The bore has been increased to provide a capacity of 1589cc to take full advantage of the International Touring Car Classification.

The Camshafts in the twin OHC head oper- ate the valves a t an angle of 80 degrees, the camshafts being driven by a Duplex roller chain from a half speed shaft gear driven from the crankshaft. The half speed shaft is located where the camshaft is on the push-rod model.

The crankshaft has been stiffened and new pattern connecting rods and pistons fitted.

The engine, which has a compression ratio of 9.9: 1, develops 97bhp at 5OOOrpm and 108bhp a t 6700rpm, with 7000rpm being the recom- mended maximum.

The sump is of cast aluminium and finned to help cooling.

3. BACKGROUND. 35 Years of Knowledge in the Twin Cam. The high performance Twin Cam has been

developed from knowledge gained by M.G. in 35 years of building sports, racing and speed re- cord cars.

This incredible marque has built up an envi- able reputation, including that of safety on the world's competition grounds since the first M.G. was built in 1923.

The M.G.A. Twin Cam is a great British challenge to the world of motor sport and, with its speed of two miles a minute and disc brakes all round, will earn M.G. a brand new name in keeping with its old tradition.

Development of the Twin OHC Engine. It is only three years since the B.M.C. 'B'

Series engine first appeared in a prototype chas- sis and aerodynamically-bodied M.G. sports Known as EX182. the car ran a t Le Mans in 1955 with distinction soon after which the production version was announced bearing the name of M.G.A.

In the Autumn of the same year, one of these cars ran a t Dundrod in the T.T. race fitted with a twin overhead camshaft head and it put up some very fast times.

A year later, in 1956, other unsupercharged twin OHC engines were fitted to the then M.G. EX179 and, at Utah, broke 62 International and

16 SAFETY FAST, April 1983 Twin Cam Group Supplement

American Class F records which included the International 200miles at 154.3 mph and the In- ternational Flying 10 miles at 170.15mph.

The engine was developed further for 12 months before being fitted to a new, stream- lined record breaker known as EX181, the most aerodynamically efficient M.G. so far.

Supercharged and with twin horizontal S.U. carburetters, the engine developed 290bhp. at 7300rpm.

With Stirling Moss at the wheel, the car travelled a t more than four miles a minute at Utah last August to create new records. The 1km record was taken to 245.64mph.

Within a year of these records comes the pro- duction version of the engine.

4. COMPETITION EXTRAS. Additional Extras for the MGA TWIN CAM. The new high performance MGA Twin Cam

will make a tremendous impact on competition circles.

In the comprehensive list of optional extras announced by the factory, there are several items of special equipment which will bring the car to peak performance for serious competitive motoring.

These include de-luxe seats which give added comfort and prevent fatigue in long dis- tance events. Specially padded on tubular frames, these seats are designed to give maximum support combined with excellent lat- eral hold.

A competition windscreen manufactured in shatter-proof plastic has also been developed. It has the same width as the standard screen but is only 6Vzins. deep thus reducing substantially the frontal area and drag a t high speeds.

Development work on tuning stages for the twin OHC engine is now in hand and a selection of alternative rear axle and gearbox ratios is av- ailable.

A wood-rimmed steering wheel is also avail- able. This has been designed along the lines of steering wheels used on Grand Prix racing cars and exclusive sports cars for many years.

An oil cooler can be provided. It will be found particularly suitable for use in hot countries or in events where high engine rpm are neededin the intermediate gears for sustained periods.

Other available equipment includes a radiator blind, adjustable steering column, ton- neau cover, twin high-note horns, windscreen washer, heater, fog lamps and radio.

PHOTOGRAPHS. A selection is available on application to the

Press Officer showing: 1. Three-warter front view of the car. 2. Under bonnet view. 3. Engine. 4. Disc brake, mounted.

STAND UP AND BE COUNTED A plea to De-luxe owners. by Jeff Wicks, Australia. Dear Phil,

You may remember that I wrote to you a couple of years ago regarding my MGA de- luxe 171BXW and that I was a Group member in 1981. At the end of that year I moved to Australia with the 'A'. My search for a deluxe while m England uncovered several cars and, on the suggestion of B.Ls. Anders Ditlev Clausager, I am endeavouring to compile a register and history of the cars. I wonder if I can impose on your enthusiasm and knowledge of the Twin Cam to help me in my search.

Details of other de-luxe owners who, likemy- self were fortunate to hold honorary member- ship of the Twin Cam Group would be invalu- able. Any other information; technical, history, suggested contacts would be greatly appreciated. The enclosed summary is a first attempt that hopefully will unearth more details. I am writing to all owners and previous owners that I know asking for their assistance. At present I have details on about l 0 cars and I hope to increase this substanially if I can find a suitable contact in the USA, the biggest de-luxe market.

Still with a total of 395 cars we have a long way to go to approach your Twin Cam register.

Any information you care to provide, no matter how seemingly trivial, would be appreciated.

Sec Note. We were able to provide details of all

known de-luxe models in Britain and those on the North American Twin Cam Registry pnnt- out, along with addresses We wish Jeff luck with his project

SUMMERY OF MGA DE-LUXE INFORMATION Dec. 1982.

The MGA De-luxe has become the accepted indentification of MGAs fitted with Dunlop centre-lock wheels and four wheel disc brakes. The de-luxe was never listed as a separate model by the factory. The Dunlop wheels and brakes were offered as a factory option and listed in contemporary sales brochures amongst the optional extras as 'Dunlop disc brakes front and rear with centre-lock wheels and roadspeed tyres'. In fact these options were only available fitted to the chassis of the by then defunct MGA Twin Cam. It is generally accepted to have been a way for the factory to use surplus chassis after the end of Twin Cam production. The early De- luxes also used twin cam bodies, easily recognised by the removeable panels in the front wheel arches. The MKII de-luxes did not have these cut-outs. The de-luxe option would seem to have been a way for the factory to use, at least initially, surplus twin cam body shells a s well as chassis. De-luxes carned standard car badges and car identification numbers.

The first de-luxe is recorded as car no. 91240 in April 1960 and production continued into the final months of MGA 1600 MkII production. The last Deluxe was 108652, while the last MGA was 109070 fimnshed on June 7th, 1962. The following production figures were supplied by Anders Ditlec Clausager. BL's Archivist at Heritage, MkI Roadster, 1960 - 50.1961 - 20 Total- 70 MkI Coupe 1960 - 4.1961 - 8 Total- 12 MkII Roadster 1961 - 116 1962 - 174 Total - 290 MkII Coupe 1961 - 12. 1962 - 11 Total - 23

Grand Total - 395 242 of the MkII roadsters were built to North

American specification. The most interesting De-luxes were six

competition coupes, the factory rally car 151ABL and the 1961 and the 1962 Sebrmg cars. 151ABL. a 16OOMkII coupe won its class in both the Monte Carlo Rally and Tulip Rally of 1962 but failed to finishin its final outing, the Liege, of the same year. By a stroke of good fortune the car survives today, it was rescued in a sorry state and largely rebuilt before the owner became aware of its history.

The two 1961 Sebring cars are accepted to have been 1600 MkI coupes and contemporary photographs show that they were badged as such. They were entered in the 1600 GT class and consequetly did not compete against the Porsche for the 1961 race. The cars finished first and second in their class

The three 1962 Sebring cars appear to have been maufactured to MM specification and were certainly fitted with the 1588cc engine to remain in the 1600cc class. The cars appeared similar to the 1961 cars except that the badges were missing and each alternate grille slat was removed to aid cooling. This year the class was once again shared with the Porsches and the MGs finished 4th, 5th and 6th in class,

I would appreciate further information on these cars or corrections to the above. With the assistance of Anders and other owners, I hope to compile a register of the cars and a more com- plete history. All contact to 10. The Moor, North Balwyn, Victoria 3104, Australia.

Further Sec. Note. We were also able to advise

Jeff of Ian Prior, owner of one of the 1962 Sebring cars, who readers of 1980 will remember took the car home from Florida.

Twin Cam Group Supplement SAFETY FAST, April 1983 17

B.M.C. Answer to Piston Problems.

During the production period of the Twin Cam a B.M.C. Service Memorandum MGl253. reputation for piston problems developed which dated 13.5.59. B.M.C. tackled in various ways, below are the details as sent out to Distributors etc. for action Sparking Plugs. To improve heat condition at

and information in the form of Service piston crown: Champion N5 plugs replaced by Memorandum. N3 type. Interchangeable in sets only.

B.M.C. Service Memorandum MGl240. B.M.C. Service Memorandum MGl278. dated 6.2.59. dated 15.9.59.

Piston Scraper nngs From Engine No 446 - Piston rings From engine No 2057* - Im- Improved design twin segment scraper rings proved design new scraper rings with expander fitted This is associated with Parts List Amend ring introduced Interchangeable ment No PMGl331 *plus engines 2043 2053,2054 & 2055

Table associated with Memorandum MGl307:

PISTON TOP SCRAPER ENGINE CHANGE PT. Pt. Lt. ASS. RING RING Comm. Finished Amend

AEH554 AEH556 AEH558 101 445 (chrome)

AEH616 AEH556 AEH615 446 605 PMG (chrome) (twin 331.

segment) 333.

*Also replace AEH556 withAEH682 and fit expander AEH680 where necessary onremainingpistonls if less than 4

beingreplaced.

AEH640 AEH649 AEH615 606 2042 (chrome) (twin ex.

segment) 2044 to 2052 & 2056

*Also replace AEH649 with AEH682 and fit expander AEH680 where necessary on remaining pistonls

if less than 4 being replaced.

AEH673 AEH649 AEH672 2043 (chrome) (twin ex. 2044 to

segment 2052 & with

expander) *Also replace AEH649 with AEH682 on remaining

pistonls if less than 4 being replaced.

AEH681 AEH682 AEH672 2251 (plain) (twin

segment with

expander)

PMG 347

PMG 371

PMG 421

REMARKS.

Use AEH681 to replace AEH554*. Use AEH682

&AEH672 in sets to replace AEH556 &

AEH558 respectively, *Also replace AEH556 &AEH558 with AEH

682 &AEH672 on remaining pistonls if less than 4 being

replaced.

Introduction of Twin segment scraper nng (6-slot type) some only fitted with expander. Use AEH to replace

AEH616*. UseAEH682 in sets to reolace AEH b f i l"it expander nno AEI I680 behind AL'H 615where necessary, or use AEH672 where replacements of AEH

615 are required.

Introduction of new top ring to reduce piston

noise. Use AEH681 to replace AEH640*. Use AEH682

in sets to replaceAEH649 Fit expander ring AEH 615 wherenecesary, or

useAEH672 where replacement of AEH61'5

is required.

Introduction of scraper ring (8-slot

type, twinsegment) with expander

Use AEH681 toreplace AEH673 Use AEH682

insets-to replace AEH649

Introduction of plain cast iron top ring as

advised above.

B.M.C.Service Memorandum MGl307. dated 23.3.60

Piston Rings. A plain cast iron top piston ring has now been introduced, replacing the chromium-plated type fitted hither to. The new ring is to improve oil consumption and is inter- changeable with both its predecessors (Part Nos AEH556 and AEH649) It is advisable that, whenever an engine calls for a replacement ring or rings, the opportunity be taken,,where necessary, of making a complete conversion to the latest type top and scraper rings. The piston and piston ring history of the engine is tabulated overleaf. Note: 2nd. & 3rd. Taper. compression rings (AEH577) remain constant from outset.

B.M.C. Service Memorandum MGl325. dated 16.8.60.

was superceded by MGl344 which was dated 19.1.61 Piston Failure. In the event of piston fai- lure attibutable to the use of fuel below 95 oc- tane a replacement set of piston assemblies pro- viding a ratio of 8.3:l should be fitted. Such pistons are now available in standard and oversizes to part No. AEH690. They are de- signed to operate with a static ignition setting of 8' BTDC and N3 sparking plugs. Accuracy in obtaining the ignition setting is again stressed (see Service Memorandum MGI 248, 296 and 301) 9.9:l compression ratio pistons part No. AEH681 will still be available but their use should be confined to competition work with 100 octane fuel, In future, the undermentioned will be supplied by BMC Service Ltd. fitted with 8.3: 1 compres- sion ratio pistons, Part No. AEH690.

Stripped engine Part No. AEH37 Half Engine Part No. AEH36 Block and Pistons Part No. AEH35.

TWIN CAM GROUP. REGALIA, DOCUMENTS & SPARES. Available from P. Richer through the Club Office, Boston upon receipt of suitable cheque payable to M.G. Car Club-Twin Cam Group.

Group Windscreen Stickers ..................... 0 . 7 5 ~ B.M.C. Rosette Stickers ........................... 0 . 6 5 ~

.......................... Group Radiator Badge £10.-00 Group Tie, Maroon, Navy or Brown .......... £3.0 Group Documant Pack .......................... £12.50 198112 Guide Addenda ......................... -. £1,00 Production History ................................. £5.00 Safety Fast Group Supplement No.l(8 pages) ................................................................. £1.5 Safety Fast Group Supplement No.2 (8 pages) ................................................................ £1.5 1983 Group Register of cars .................... £1.5 1983Guide Addenda ............................... £2.0 25th. Anniversary Booklet ...................... £5.00 25th. Anniversary Poster .......................... £1.0 Floorboard Screws set ............................ £4.50 Trim-Screws set Roadster 0 . 7 0 ~ Coupe . £1.40 Grab handle screw &nut set .................. '£1.50 Orders taken for Fume Excluders ........... €12.5 Anniversary Raffle Tickets, book of 5 .......... 5Qp AlfreeGroup sticker with 5 books ............ £2.5

Please add 50p for Overseas orders marked * to go towards extra m a h g charges, and £ 25 if re-g Ai~Mad services For documents add a single surcharge only for more than one item

Twin Cam Group Supplement