Valve seat insertsTechnical Information andInstallation Instructions

2

Index

Chapter 1: Introduction

1.1 Valve seat installation

1.2 Machining practices

Chapter 2: Cutting valve seat inserts andcounter bores

2.1 Removal of valveseats and cuttingof seat pocketcounter bores

Chapter 3: Installation

3.1 Inserting thevalve seats

3.2 Cutting theseating surface

3.3 Using acutting machine

3.4 Using agrinding machine

3.5 Checking thefinal product

Chapter 4: Dura-Bond valve seat inserts

4.1 Valve seat insertsMaterials

4.2 30000 / 70000 Series

4.3 Overview

id Valve Seal Catalog 9/18/01 10:44 PM Page 4 (Black plate)

1.1 Valve seat installation

Valve seat installation and refitting isonly one of many operations neces-sary for the professional rebuildingor reconditioning of a cylinder head.Successful cylinder head remanu-facturing requires that these recon-ditioning operations be done in thecorrect sequence.Valve seat installation and refittingcan only be successfully accom-plished after the following operationshave been completed.• Through cleaning, inspection

and any failure analysis

• Measure and record each as-sembled valve stem height andvalve head protrusion

• Straightening of the cylinderhead and milling/grinding of thefiring deck and all other matingsurfaces

• All valve guides must be rene-wed or refitted and be withinoriginal factory specifications

The cylinder head must be dimen-

sionally and geometrically withinoriginal factory specifications. Thecylinder head thickness, valve gui-de clearances, concentricity, andperpendicularity must be correct.There should be no warping, twi-sting, or any type of misalignmentof any part of the cylinder head.Sometimes you may lightly touchup the valve face and valve seatmating surface without putting thevalve geometry out of factory spe-cification but most of the modernmulti-valve aluminum cylinderheads will require new inserts beinstalled to maintain correct valvetrain geometry.Only new valves or valves whichhave been reconditioned and arewithin original factory specificationmust be used. All valve springsmust be inspected and must meetall original factory specifications orbe replaced.As it relates to valve seats, thereare three types of cylinder heads:

• Cast iron cylinder heads withremovable valve seat inserts

• Cast iron cylinder heads withintegral hardened valve seatareas

• Aluminum cylinder heads withremovable valve seat inserts

You must replace the old valve seatinsert or refit the integral hardenedvalve seat area with a new valveseat insert if:• The cylinder head required

straightening before resurfacing.

• Any welding had to be done onthe cylinder head.

• The cylinder head is aluminumand was cleaned in a heatingoven.

• The valve seating (mating) sur-face has receded beyond factoryspecifications.

• The valve seating (mating) sur-face is too wide and recutting orregrinding would lower the seatbeyond factory specifications.

• The integral seat of a cast ironhead has been ground before.(The depth of the hardened cy-linder head material used for theseating area will be too shallowto allow a second grinding)

• There is any evidence that thevalve seat insert is loose in thecounter bore pocket, or does nothave adequate interference fit.

• There is any evidence of corrosi-on of the cylinder head materialaround the outside diameter ofthe valve seat insert.

• There is any evidence that theseat has any cracking, burning,pitting or fissures.

• The fuel type being used is goingto be changed. This will require ahigher duty range valve seat forbetter durability.

Chapter 1: Introduction

Picture 2

1.2 Machining practices

Although many factors contributeto the successful machining ofvalve seats. Here are several keyconditions that are required toachieve good results.• By far the most important is to

have properly sharpened toolsand properly dressed grindingstones.

• Keep your tooling setup as”short and tight” as possible toassure rigidity (Picture 1). Theless deflection in the tooling themore accurate the dimensionsof the cut and the greater con-centricity.

• Keep your clamping arms andfixtures in good repair for correctgripping.

• Make sure not to distort or put atwist into the cylinder head whenclamping to a fixed rail cylinderhead holding fixture (Picture 2).

• Use the correct size pilots, whichmust be straight.

• Use the correct spindle speedsand feeds.

Picture 1

id Valve Seal Catalog 10/22/01 8:31 AM Page 8

5

2.1 Removal of valve seats andcutting of seat pocket coun-ter bores

Replacing valve seats in heads withremovable seat inserts can be donein several ways, but the method werecommend is to use a cutter slight-ly smaller than the outside diameterof the existing valve seat insert andcut the old seat out (Picture 3). Stopcutting just as the old seat insertbegins to rotate. The thin wall of theold valve seat insert can now be ea-sily removed (Picture 4).

Some machinist will install a newinsert in the existing seat pocketwithout recutting the counter bore.Although this method can be usedon some large cast iron cylinderheads which are thick walled, it isnot a recommended procedure formost automotive or ”light pattern”cylinder heads. It is much betterto cut a new seat insert counterbore for better valve life and valve

DuraBond recommends the following press fittings:

Outer diameter valve seats inserts Material cylinder head cast iron Material cylinder head aluminium[inch] [mm] [inch] [mm] [inch] [mm]

0.7874 - 1.1811 20 - 30 0.0031 0,08 0.0047 0,121.1811 - 1.5748 30 - 40 0.0043 0,11 0.0059 0,151.5748 - 1.9685 40 - 50 0.0051 0,13 0.0071 0,181.9685 - 2.3622 50 - 60 0.0063 0,16 0.0079 0,202.3622 - 2.7559 60 - 70 0.0071 0,18 0.0087 0,22

When machining the seat pocketcounter bore in a cast iron cylindercast iron cylindercast iron cylindercast iron cylindercast iron cylinderheadheadheadheadhead we recommend a cutting

speed of 100 to 250 RPM100 to 250 RPM100 to 250 RPM100 to 250 RPM100 to 250 RPM with nocutting oil. When cutting a seatpocket counter bore in aluminumaluminumaluminumaluminumaluminum

cylinder headscylinder headscylinder headscylinder headscylinder heads we recommendusing a cutting oil and a spindlespeed of 400 to 600 RPM400 to 600 RPM400 to 600 RPM400 to 600 RPM400 to 600 RPM.

Picture 3 - Cutting valve seat inserts

seat insert retention in the cylinderhead (Picture 5). This will also in-sure concentricity and perpendicu-larity with the valve guide and willprovide a fresh metal surface forbetter heat transfer (see our recom-mended interference fit chart for thecorrect outside diameter).

Picture 4 - Removing the thin wall of theold valve seat insert

Picture 5 - Cutting the counter bore

Chapter 2: Cutting valve seat inserts and counter bores

Outer diameter valve seats inserts Material cylinder head cast iron Material cylinder head aluminium[inch] [mm] [inch] [mm] [inch] [mm]

0.7874 - 1.1811 20 - 30 0.0031 0,08 0.0047 0,121.1811 - 1.5748 30 - 40 0.0043 0,11 0.0059 0,151.5748 - 1.9685 40 - 50 0.0051 0,13 0.0071 0,181.9685 - 2.3622 50 - 60 0.0063 0,16 0.0079 0,202.3622 - 2.7559 60 - 70 0.0071 0,18 0.0087 0,22

id Valve Seal Catalog 10/15/01 2:37 PM Page 11

Replacing valve seats in cylinderheads with integral seats will requirea new seat pocket counter bore tobe cut. The approximate outside dia-

meter for the replacement seat is.100”(2,5 mm) larger than the valve headdiameter. The inside diameter of thereplacement seat is approximate-

ly.100” (2,5 mm) smaller than thevalve head diameter. The depth isusually .188” to .250” (4,7 – 6,4 mm).These sizes are guidelines only.

Many of the newer cylinders do nothave the room to install seats withOD’s larger than the OD of the valve(see our recommended interferencefit chart for the correct outside dia-meter).

All counter bores must be concen-tric with the valve guide, have astraight wall, flat bottom and be wi-thin .0005” (0,013 mm) of correctsize and be round.

0.188 - 0.25“4,7 - 6,4 mm

0.1“2,5 mm

0.1“2,5mm

6

id Valve Seal Catalog 9/18/01 10:46 PM Page 10 (Black plate)

3.1 Inserting the valve seatsBefore pressing in the new valveseat insert please be sure:• Verify that the valve seat dimen-

sional measurements are correct

• Verify the counter bore measure-ments are correct

• Make sure there are no chips ordebris in the counter bore

• Use a seat installation tool toinsure that the valve seat is inser-ted squarely into the counterbore pocket (Picture 6).

• Use a flat and square seatdriver tool whose size is justslightly smaller than the outsidediameter of the valve seat in-sert (Picture 7).

• Use a correct size pilot for thevalve guide, when using thisvalve seat driving tool.

Picture 6

Picture 7

For Dura-Bond valve seat inserts:

• Insert the valve seat with the.radius side down.

• Because of the smooth radiuson the bottom outside edgeand the compressive “springaction” of the material, shrin-king of the seat using liquid nitrogen -and heating the cy-linder head is not necessary is rprior to insertion the cylinderhead.

cobalt alloyLess force required - less chanceof damaging seat counter bore.

cast iron

30000 Series

chrome alloy nickel alloy

70000 Series

valve seat material

inse

rtio

n fo

rce

req

uire

d to

inst

all

into

cyl

ind

erhe

ad [%

]

Chapter 3: Installation

3.2 Cutting the seating surface

Check the engine specificationmanual for the correct assembledvalve height, valve protrusion, seatangles, seat widths and any otherspecial seat requirements. Thesefactory specifications are importantto maintain the correct valve lash,

compression ratios, clearances bet-ween valves and pistons, and thegeneral overall valve train geometry.Machining and assembling the cy-linder head to the original manufac-tures specifications is critical for thecorrect operation of the engine.

3.3 Using a cutting machine(Picture 8)

• Select a cutter profile matchingthe original factory valve seat.The top and bottom relief angles,and the seating surface width andangle must match the designcalled for by the original enginemanufacture for the valve traingeometry to be correct.

• Select the type and grade of car-bide best suited for the hardnessof the valve seat being machined.

• Make sure that the tool is sharpand has the correct rake anglesand relief angles.

• A 5-degree cutting rake anglewith an 11-degree relief or clea-rance angle is generally foundto be best for valve seats up to1.250” (31,8 mm) in diameter.

• A 3-degree cutting rake anglewith a 7-degree relief or clearan-ce angle is generally found tobe best for cutting valve seatslarger than 1.250” ( 31,8 mm) indiameter.

• Select the correct spindlespeed for the type of seat beingcut.

• A spindle speed of 150 to 450RPM is generally a good speedfor cutting the valve seat insertless than 1.500” (38,0 mm) indiameter.

• A spindle speed of 100 to250 RPM works best for seatslarger than 1.500” (38,0 mm)in diameter.

• Dura-Bond finds that most peoplewho have the drill press style of machine, like the 50 - 100 RPM

• Set the cutter bit to the correctsize for the valve being usedaccording to the factory repairmanual.

• Cut the seat depth to match thecorrect assembled valve height.

Outer Diameter valve seat insert Tool RPM [inch] [mm] relief angle cutting angle [1/min]

< 1.250 < 31,8 11° 5 ° 150 - 450> 1.250 > 31,8 7 ° 3 ° 150 - 450< 1.500 < 38,0 7 ° 3 ° 150 - 450> 1.500 > 38,0 7 ° 3 ° 100 - 250

Picture 8

8

Outer Diameter valve seat insert Tool RPM [inch] [mm] relief angle cutting angle [1/min]

< 1.250 < 31,8 11° 5 ° 150 - 450> 1.250 > 31,8 7 ° 3 ° 150 - 450< 1.500 < 38,0 7 ° 3 ° 150 - 450> 1.500 > 38,0 7 ° 3 ° 100 - 250

id Valve Seal Catalog 10/15/01 2:37 PM Page 6

3.4 Using a grinding machine

• Select the correct size of stonefor the valve being used.

• Select the correct type of stonefor the hardness level of valveseat.

• Dress the stones as needed tothe angles specified in the repairmanual.

• Grind the seating angle first

• Grind the top relief angle to adjustseat height

• Grind the bottom relief to adjustthe seat width.

Adjustments to these grinds will benecessary to achieve the correctassembled valve height and seatwidth.

Also, in general, for valve seats inthe 1.375“ to 2.125” (35,0 – 54,0 mm)diameter range, if no specific facto-ry specifications are available, a ge-neral guideline is to make the valveface to valve seat contact area widthbetween .040”-.060” (1,0 – 1,5 mm)for the intake and .060”-.080” (1,5 –2,0 mm) for the exhaust. For valveseats smaller than 1.250” (31,8 mm)the seat widths will be reduced byone half the values listed above.For engines using LPG, the exhau-st seating width should be .100”(2,5 mm).

Wider seating widths will give agreater area of surface contactwhich will give better cooling ratesbut the larger contact area will re-duce the pounds per square inchsealing pressure, so too large of acontact area will cause seats to

3.5 Checking the final product

• Check the sealing by using avacuum check

• Check the seating position byusing Prussian blue on the valveand seat

• Check for the correct assem-bled valve stem height and val-ve head protrusion

0.015 - 0.030“0,4 - 0,8 mm

0.04 - 0.08“1,0 - 2,0 mm

Inlet: 0.04 - 0.06“ / 1,0 - 1,5 mmExhaust: 0.06 - 0.08“ / 1,5 - 2,0 mm

In general, if no factory specificati-ons are available, remember tokeep the valve face and valve seatcontact area to the outer limits ofthe valve head diameter. Dependingon the valve head diameter thiscontact area will be .015” to .030”(0,4 – 0,8 mm) in from the outsidediameter of the valve head. If theseating contact area is too closeto the valve steam you will impe-de the gas flows and build up heaton the exhaust side and possiblyrestricted power due to less air andfuel getting into the combustionchamber on the intake side. Youwill get better heat transfer awayfrom the exhaust valve and into the

water jacket if you keep the con-tact area to the outside diameterof the valve head. But you mustnot take it to the extreme outsidediameter or you will ”burn” the val-ve and seat prematurely, becausethere will be too much heat concen-trated at the very edge of the val-ve.

”burn” due to gas leakage. Too thinan area will cause high mechanicalabrasion forces and high operatingtemperatures and will ”wear” theseating area faster than normal.

9

id Valve Seal Catalog 9/18/01 10:44 PM Page 5 (Black plate)

Chapter 4: Dura-Bond ® Valve Seat Inserts

4.1 Valve seat inserts

Materials

Modern engines put much higherlevels of thermal and mechanicalstress on valve seat inserts. Tohandle the more severe conditionswithin these new generations ofengines, the OE-Manufacture isequiping them with high tech sin-tered valve seat inserts. The normalcast iron valve seat will not adequa-tely withstand the demands of thisnew engine environment.

This is the reason why Dura-Bond offers high tech sintered valve seats in two specificationsto be used for the complete rangeof today’s engines and the engines of the past and of the future.

4.2 30000 / 70000 Series

• 30000 (Gold) Series High Machinability

This sintered insert offers a blend of finely dispersed tungstencarbide residing in a matrix of tem-pered tool steel and special alloy ironparticles. With this blend, the 30000series represents a superb combi-nation of good hardness and good

machinability. The machinability iscomparable to cast iron, and this30000 series shows good wear and heat resistance.

This very machinable materialis designed for naturally aspiratedand turbocharged engines in thelight to upper duty range.

• 70000 (Diamond) Series High Temperature Resistance

This specification has very highheat resistance which will remaineven at very high temperatures.The sintered insert is made outof a high speed tool steel (tungstencarbide). This insert also has cera-mic like characteristics, which giveit very high temperature resistance.It has special additives blendedinto the matrix which impart hightemperature lubricant properties tothe valve seat. This solid lubricantenables this material to be used indry fuel applications, such as pro-pane, LPG and natural gas. Theyprevent the microwelding of the val-ve seat material to the valve face.

This eliminates the primarycause of valve seat erosion andfailure. This very high heat andwear resistant seat is desi-gned for propane, LPG and naturalgas engines, as well as for highperformance engines, heavy dutyand extremely duty applications.

4.3 Overview

Dimensional specifications must beevaluated in order to assure correctselection of valve seat whenever en-gine parts are being selected. Hea-vy duty or extreme service appli-cations should be considered to

assure that the individual enginerebuilder’s standards are met andare the responsibility of rebuilderto determine suitability.

30000 Series

(High Machinability) (High Temperature Resistance)

Fuel type petrol (unleaded), diesel propane, LPG, natural gas, petrol (unleaded), diesel

Cylinder head Material aluminium, cast iron aluminium, cast ironApplications turbocharged engines, heavy and extreme duty range

aspirated engines, high performance engines,lower to upper duty range all gas engines (propane, LPG)

70000 Series30000 Series

(High Machinability) (High Temperature Resistance)

Fuel type petrol (unleaded), diesel propane, LPG, natural gas, petrol (unleaded), diesel

Cylinder head Material aluminium, cast iron aluminium, cast ironApplications turbocharged engines, heavy and extreme duty range

aspirated engines, high performance engines,lower to upper duty range all gas engines (propane, LPG)

70000 Series

id Valve Seal Catalog 10/22/01 9:36 AM Page 2