Training Manual

INDEX:CHAPTER 1 - GASKET DEFINITION, FUNCTION AND PURPOSE

1. Basic Operating Conditions

I Bolt LoadII Flange Loading and BendingIII TemperatureIV Thermal Distortion and VibrationsV Internal PressureVI Sealed Medium (Fluid and Gases)

2. Sealed Mediums

I Combustion ForcesII Fluids

3. Surface Characterisitics and Clamping Loads

I Surface FinishII Minimum Seating StressIII Critical Sealing Stress

4. Gasket Materials Requirements and Properties

I Compressibility and RecoveryII Tensile StrengthIII Temperature Resistance and EffectsIV Dimensional StabilityV Crush ResistanceVI Creep RelaxationVII Impermeability and SealabilityVIII Thermal ConductivityVIIII Handling Characteristics and Shelf Life

GASKETSENGINE SEALING SPECIALIST

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5. Purpose and Function of Gasket TypesI Cylinder Head GasketsII Cylinder Head Gasket DesignsIII Intake Manifold GasketsIV Exhaust Manifold GasketsV Rocker Cover GasketsVI Oil Pan GasketsVII Miscellaneous Fibrous GasketsVIIII Valve Stem SealsIX Rear Main Bearing Seals

6. Coatings, Embossments, and Sealing BeadsI CoatingsIl EmbossmentsIII Sealing BeadsIV Chemical Sealants

CHAPTER 2 - ROL: DESIGN & MATERIALS TECHNOLOGY

I Cylinder Head GasketsII Premium Valve Cover and Oil Pan GasketsIII Seals - Oil Seal & Valve StemIV Intake Manifold GasketsV Intake Manifold Valley Pan GasketsVI Exhaust Manifold GasketsVII Miscellaneous Gaskets

CHAPTER 3 - SET CONTENTS

I HG - Head GasketsII HS - Head SetsIII FS - Full SetIV LS - Lower SetV VS - Valve CoverVI MS - Manifold Sets/Plenum GasketsVII OS - Oil Pan SetVIIII TS - Timing Cover SetIX Miscellaneous Gaskets (GB - DS - CM - EG - GR - FP)

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CHAPTER 4 - SEALING THE VALVE COVER

I. Valve Cover Gaskets

I Cork CompositionII Cork ElastomerIII ROL HI-PER BLUEIV Molded Rubber

2. Choices When You Need Them

3. Installation Tips

CHAPTER 5 - PREVENTING HEAD GASKET FAILURE CAUSED BYDETONATION

1. Whats Detonation

2. Cylinder Heat and Pressure

3. What Causes DetonationI Excessive Compression RatioII Over Advanced Engine TimingIII Glow SpotsIV Low Octane FuelV Lean Air/Fuel MixtureVI Incorrect Spark PlugsVII Inefficient Cooling System/Engine OverheatingVIII Malfunctioning EGRIX Engine Lugging

4. Eliminating Detonation

5. The Role of the Head Gasket

6. ROL High Temperature Head Gaskets

CHAPTER 6 - CYLINDER HEAD GASKET INSTALLATION

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GASKET DEFINITION, FUNCTION AND PURPOSE

CHAPTER 1

A gasket is a material or combination of materi-als that is secured between two separate membersof a mechanical joint. Its function is to effect a sealbetween the members (also called flanges) andmaintain the seal for a prolonged period of time.

The gasket must be capable of sealing the mat-ing surfaces, resistant to the medium being sealed,and have the ability to withstand the application

temperature and pressure. The basic factor in thecreation of the seal is sufficient stress on the gasketto insure its conformation to the flange surface. Thisblocks the passage of the medium between thegasket and the flange. In addition, this stress mustbe high enough to close any voids in the basicmaterial if it is to block passage of the seal medium.

Gaskets are used at almost every joint of an engine. The following exploded engine views illustratetypical gasket types and locations.

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1. Air cleaner mounting gasket2. Carburetor mounting gasket3. EGR valve gasket4. Water outlet/Thermostat housing gasket5. Intake manifold gasket6. Timing cover gasket7. Camshaft front seal8. Timing cover seal9. Repair sleeve10. Water pump mounting gasket11. Oil pump mounting gasket12. Valve cover gasket13. Valve stem seals14. Cylinder head gasket15. Exhaust manifold gaskets16. Exhaust flange gasket17. Distributor mounting gasket18. Fuel pump mounting gasket19. Rear main seals20. Oil pan gaskets21 Oil drain plug gasket

1. Air cleaner mounting gasket2. Carburetor mounting gasket3. EGR valve gasket4. Water outlet/Thermostat housing gasket5. Intake manifold gasket6. Timing cover gasket7. Camshaft front seal8. Timing cover seal9. Repair sleeve10. Water pump mounting gasket11. Oil pump mounting gasket12. Valve cover gasket13. Valve stem seals14. Cylinder head gasket15. Exhaust manifold gaskets16. Exhaust flange gasket17. Distributor mounting gasket18. Fuel pump mounting gasket19. Rear main seals20. Oil pan gaskets21. Oil drain plug gasket22. Auxiliary shaft seal

TYPICAL V6 ENGINE GASKET AND SEAL LOCATIONS

TYPICAL L4 ENGINE GASKET AND SEAL LOCATIONS

1

23

17

5

5

1412

1316

1815

4

1919

20

20 21

9

8

6

7

11

10

1

2

3

10

5

17

14

4

1315

16

18

12

7

19

1919

9822

2111

6

6

2020

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1. Air cleaner mounting gasket2. EGR valve gasket3. Carburetor mounting gasket4. Valve cover gasket5. Exhaust flange gasket6. Intake/Exhaust manifold gaskets7. Water outlet/Thermostat housing gasket8. Valve stem seals9. Push rod cover gasket10. Cylinder head gasket11. Distributor mounting gasket12. Oil pump mounting gasket13. Rear main seals14. Water pump mounting gasket15. Timing cover gasket16. Timing cover seal17. Repair sleeve18. Oil pan gaskets19. Oil drain plug gasket

1. Air cleaner mounting gasket2. Carburetor mounting gasket3. Water outlet/Thermostat housing gasket4. Water bypass gasket5. Intake manifold gasket6. Push rod cover gasket7. EGR valve gasket8. Valve cover gasket9. Valve stem seals repair sleeve10. Exhaust flange gasket11. Exhaust manifold gaskets12. Cylinder head gasket13. Distributor mounting gasket14. Timing cover gasket15. Water pump mounting gasket16. Rear main seals17. Fuel pump mounting gasket18. Repair sleeve19. Oil pump mounting gasket20. Oil pan gaskets21 Oil drain plug gasket22. Timing cover seal

TYPICAL L6 ENGINE GASKET AND SEAL LOCATIONS

TYPICAL V8 ENGINE GASKET AND SEAL LOCATIONS

1

2

3

10

5

17

14

4

13

16

18

12

19

9

11

67

8

1315

18

1

2

3

5

14

13

1618

19

11

67 8

15

9

16

2120

20

22

17

12

10

4

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Basic Operating Conditions

Bolt Load

Cylinder head bolts have to absorb a portion ofthe combustion force developed by pressure load-ing and maintain sufficient clamping force toexceed the minimum stress on the gasket for agood seal. The dynamic stress felt by the headbolts must be within the endurance fatigue strengthof the bolt or else fatigue failures may occur.

When a bolt is tightened, 80 to 90% of the tight-ening torque overcomes the friction in the threadand under the head. Only 10 to 20% is actual bolttension. Even if bolt torque is measured very accu-rately, variations in friction or error in the estimateof friction can cause large differences between cal-culated bolt load and actual bolt load.

The variables in friction are caused by type andamount of lubricant, thread cleanliness and surfacecondition, fastener grade and hardness, and non-parallel flange surface under the bolt head.Additionally, some of these variables change whenthe components are reused.

Flange Loading and Bending

For a gasket to seal it must have the properamount of load applied to the flange. In mostflange assemblies, the distribution of force aroundthe gasket is not the same at all points. In order toequalize the distribution of load on the gasket, agreater number of properly spaced bolts should beused. In todays light weight engines, it is notalways possible to have rigid flanges and when

flange loading occurs, the flange will bend or bowbetween the bolts.

Temperature

Operating temperature of an engine is a criticalfactor to consider in the operation of a gasket, par-ticularly the head gasket. The head gasket mustseal hot combustion pressure and fluids. The cylin-der wall and combustion chamber temperaturechanges rapidly, and the engine hardware, thatare made of different materials, expand and con-tract. This causes the loading on the bolts and con-sequently the gasket, to vary. The gasket must besufficiently resilient to accommodate fluctuation intemperature as low as 240 degrees F for coolant

The gasket must be able to hold a seal between the bolts eventhough the flange is bowed. The thicker and softer a gasket is, themore bending and distortion it can tolerate.

ROL HI-PER BLUE and premium cork/rubber valve cover gasketsseal well under light load and are available in optional thickness ofup to 5/16 to accommodate valve cover bowing and distortion.

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and as high as 2200 degrees F in the combustionchamber. The materials used in ROLs HighTemperature head gaskets offer the highest level ofheat resistance in the industry.

Thermal Distortion and Vibrations

Distortion and uneveness occurs because of thehigh temperature of many engines, the weakness incastings and covers, uneven bolting patterns andbolt tightening sequence. Heating and coolingcycles will cause thermal expansion in flanges, par-ticularly cylinder head and exhaust manifolds. Forengines that are subjected to high vibrations ROLoffers gaskets that are steel reinforced or have lowfriction facings or coatings to prevent extreme wearon gasket surfaces.

Internal Pressure

Internal pressure can create enough load on thebolts and flanges to cause a blowout. If the pres-sure is great enough the bolts and flanges willexhibit distortion such as elongation. This elonga-tion could be in addition to that caused by the ini-tial tightening process. The flange might deflect orbow because of internal pressure in addition to thedistortion caused by the initial bolt loads.Combustion pressures in the cylinder can cause thehead to move. If the cylinder head is not held tight,hot combustion gases will leak by the gasket and burn it.

Sealed Medium (Fluid and Gases)

The science of sealing becomes extremely com-plicated when a variety of medium are to be sealedat the same time. For example, a cylinder headgasket must seal high pressure combustion gases,crankcase oil and engine coolant. The gasketdesign and materials must be impervious to thegases, fluids, and temperature. The gasket must sealvery high unit loading around the combustion open-ings and lower loading around oil and water passages.

A good example is the ROL Tork-Cork steel reinforced valve covergasket pictured above for the Ford 2.3L HSC engine.

Right: On this ROL gasket for big block Chevrolet engines, thecombustion chamber rings are made out of stainless steel for max-imum heat resistance while the soft silicone beading aroundcoolant and oil passages require less torque load to seal.

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Sealed MediumsCombustion Forces

Combustion forces and compression must becontained in the cylinder during the power andcompression strokes of the engine. Any leaksbetween the cylinder head and block will causepoor engine performance. The combustion gaspressure acts on a large area of the cylinder headface. Movement of the face can occur if the cast-ing design of the head does not give sufficient sup-port to the combustion face area.

Fluids

Fluids such as oil and antifreeze must be sealedand metered in an engine. In many head gasketapplications the size of the oil and coolant holesdiffer greatly from the size of the correspondingpassage in the head or block. This size differenceexists in order to meter, or control, the speed andvolume of the medium being sealed.

Wicking and wetting must be controlled to a rea-sonable degree. A poorly constructed gasket mayleak in one of two ways; the fluid may seep its wayalong the flange and gasket interface, or it maypermeate through the gasket material. There is aminimum initial compression stress that is necessaryto insure that the gasket conforms to the face of theflange, and to close the structure of the gasketmaterial to the sealed fluid at the required pressure.Major factors effecting minimum sealing stress are:

gasket material internal fluid pressure viscosity of the fluid width and thickness of the gasket surface finish of material and flange faces flange design and outline

Consideration must also be given to the type offuel, oil, or coolant that the gaskets will seal, andwhether the gasket edge will be permanentlyimmersed in such liquids or only occasionallysplashed by them. Some materials that have idealtorque retention properties will deteriorate rapidlyif exposed to certain fluids.

Surface Characteristics andClamping LoadsSurface Finish

Surface finish of a gasket joint is an importantconsideration. Normally the smoother the flangesurface is, the better the seal. Flange surface fin-ishes range from a rough casting to smooth finishesproduced by machine lapping. Each type of sur-face influences the degree of sealability. Smoothersurface finishes require a minimum stress to the gas-ket material in order to obtain the seal. Rougherfinishes with the same gasket material produce lesssealability. A seal is effected by compressing and

On this small block Ford gasket ROL reduces the size of the waterpassage to slow the coolant flow helping to keep the engineoperating cooler.

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flowing the gasket material along the surface con-tour.

Minimum Seating Stress

The compression stress required to adequatelyconform the gasket to the flange face and securean initially perfect seal is known as the minimumseating stress. The stress, measured in PSI over awide area, is different with various materials.Factors effecting minimum seating stress include:

load required to reach critical sealingstress of the material

internal pressure to be sealed

creep relaxation of the gaskets

load change due to thermal expansionand contraction

number and spacing of bolts

flange flexibility

crush strength of the gasket material

Critical Sealing Stress

The critical sealing stress is a function of the gas-ket material. It is the minimum load required to closethe pores (or air cavities) of the gasket material tocontain the fluid or gases within an acceptablelevel.

Gasket Materials Require-ments and Properties

Compressibility and Recovery

The gasket material is compressed under con-stant load. The loss in thickness under load iscalled compressibility, expressed as a percentageof original thickness. The percentage of lost thick-ness that is gained upon removal of a load isreferred to as percent recovery. These values are ameasure of the conformability of the material andits ability to push back and maintain a seal.Recovery is the ability of the gasket to overcomeeither load loss in the bolt or dynamic deflectioncaused by heat distortion.

Tensile Strength

This characteristic relates to the pressure within theassembly that the gasket can seal. Blowout resistanceis primarily a function of tensile strength. Wall widthand sealing stress (or unit load) are considerations.

CYLINDER HEAD FLATNESS ANDSURFACE FINISH RECOMMENDATIONS

OUT OF FLAT LENGTH WIDTHRECOMMENDEDMAXIMUM

V-6 ENGINES .003 .002V-8 ENGINES .004 .0026 CYL. ENGINES .006 .002

SURFACE FINISH

RECOMMENDED MAXIMUM 125 MICRO-INCHESRECOMMENDED MINIMUM 60 MICRO-INCHESPREFERRED RANGE90 TO 110 MICRO-INCHES

Many gaskets, like this ROL oil pan gasket for the Chrysler 3.8Lengine, are steel reinforced to avoid blowouts due to internal pres-sure or vacuum of the medium being sealed

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Temperature Resistance and Effects

In maintaining an effective seal, temperaturescan never be considered a completely indepen-dent factor. The interaction of temperature withtorque loss goes together. As temperature risesfrom the initial ambient conditions under which thejoint was tightened, the seal usually improves by aperceptible degree. This is caused by a softeningeffect to the gasket. The gasket flows into flangesurface imperfections, thereby improving the initialconformation between the gasket and flange.

Conformation can also be enhanced by thedifference in thermal expansion between non-metallic gaskets and flanges. With this high coeffi-cient of expansion, gaskets expand against therestraints of the flange, therefore, increasing flangepressure. Too high heat can deteriorate a chosenmaterial. Prolonged exposure to temperature cancause many nonmetallic materials to harden.

Dimensional Stability

This characteristic is very important becausegaskets can change in shape or dimension from adry to a moist state. Any change after cutting andassembly will cause a gasket to not fit the flangesproperly and alignment will not be correct.Dimensional stability can be measured in a givendirection usually quoted in a percentage of change.The dimensional stability of materials that have a grain

is usually better along the fibers than across them.

Crush Resistance

When a gasket is placed in a joint and com-pressed, the gasket may extrude, creep, and relax.If the fasteners are tightened further, either the fas-teners, the flange or gasket will ultimately fail. Ifany gasket is subjected to extremely high loading itwill crush. The crush resistance of a gasket materi-al is its ability to resist compression and is deter-mined by the formulation of the material. Thebinder material, usually a rubber or other polymerblend will affect crush resistance.

This gasket was exposed to prolonged heat as a result of lowcoolant fill and engine overheating resulting in deterioration of thefacing material.

On very soft gaskets like this silicone oil pan gasket for late modelChevrolet small blocks ROL installs torque limiters to prevent over-tightening.

Over-tightening destroyed this gasket.

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Creep Relaxation

When a gasket is clamped between two flangesto make a seal, the gasket acts like a compressedspring and presses against the flanges and bolts.The bolts and flanges in turn, act like springs andpress against the gasket. It is this balance betweenforces supplied by bolts, flanges, and gaskets thatkeeps the bolt tight and the joint sealed. This bal-ance must be substantially pressured to maintainthe sealed joint. In reality, this balance changessomewhat do in part to creep relaxation of the gas-ket material. Creep is cold flow creeping or thin-ning down of material spring stiffness resiliency.Creep relaxation occurs due to fatigue, heat, pres-sure, or mechanical vibrations. The magnitude ofthe effect depends on the exact gasket formulationand how the material responds to elevated operat-ing temperature.

Impermeability and Sealability

This property relates to leakage through thegasket. Materials such as metal and rubbers areimpermeable. Other gasket materials are madefrom fibers, polymers, and a variety of other ingre-dients that when combined result in a compositionwith pores. Fluids will migrate and pass throughthese materials. ROL engineers specify high quali-ty materials according to engine needs.

Thermal Conductivity

In some smaller compact engines there is needfor gaskets to have little thermal conductivity or tobe an insulator. Some gaskets must thermally insu-late the carburetor or fuel tank from a heat source.The gasket needs to be of a material that will nottransfer the heat to an adjacent flange. Mostresilient gasket materials are good insulators rela-tive to the metal parts of an assembly.

In other instances, particularly cylinder headgaskets, a higher level of thermal conductivity isbeneficial. Materials such as expanded graphite

CREEP RELAXATION

LOSS(EXAGGERATED)

Gaskets such as this ROL valve cover gasket for small block Fordsare made of silicone and are impermeable by engine oil.

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are known as anisotropic materials, which meansthey transfer heat laterally. In the case of a headgasket this results in quicker and more effectivetransfer of combustion chamber temperature to thecoolant, resulting in reduced hot spots and loweroperating temperatures. All ROL High Temperaturehead gaskets are made with expanded graphitefacings.

Handling Characteristics and Shelf Life

All gaskets must be made so that the materialdoes not change significantly while the gasket isbeing handled and stored. It has to withstand han-dling as would be encountered during installation.It is important, during a prescribed amount of time,that the gasket material maintain its original pre-scribed characteristics. Many cheaper no-namevalve cover gaskets will shrink sitting on the shelf.

ROL premium valve cover gaskets are a special-ly blended combination of cork and rubber. ROLpremium valve cover and oil pan gaskets will notshrink.

Purpose and Functionof Gasket Types Cylinder Head Gaskets

The most critical sealing application in anengine is the cylinder head gasket. It must simulta-neously seal:

high combustion temperatures and pressures

water and antifreeze with their high wickingand wetting characteristics

lubricating oil with its associated detergentsand variable viscosities

A head gasket must perform in temperatureranges of well below zero at start up, to over 400degrees Fahrenheit during operation. In addition,the head gasket must seal peak combustion tem-peratures that exceed 2000 degrees F and with-stand peak pressures of 1000 psi in spark ignitionengines and 2300 psi in turbocharged dieselengines.

Head gaskets must resist the forces that scuffgasket sufaces and compromise sealing. Enginevibration and head shifting and flexing all resultfrom combustion pressures.

Another factor affecting sealing is the differentexpansion rates of bi-metal (aluminum head andcast iron block) engines. Aluminum expands atabout twice the rate of cast iron. The unevenexpansion rates create a shearing action that thehead gasket must accommodate. Head gasketsmust also resist crushing from cylinder clampingforces that may be unevenly distributed across thehead.

This ROL carb mounting gasket is made of compressed cellulousfiber material to reduce heat transfer from the engine to the fueldelivery system.

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In todays engines sufficient bolt loading is aproblem because of lighter weight castings andsmaller cylinder blocks. Bolt spacing is inadequatedue to the use of more Siamese cylinder configurations.

In-line engines present difficult head gasket seal-ing because of unbalanced bolt loading. Gasketdesigners use many different methods to combatthis problem. Many designs use embossments,coatings, and chemical beading for extra loading.Each of these methods is an attempt to obtain morebolt load in the pushrod area.

Each engine design has its own factors to beconsidered when designing a cylinder head gas-ket. These include:

bolts, number and distribution length, use ofwashers, specification and quality

clamping load (applied load and loaddistribution)

temperature (range, influence of enginedesign, operating conditions)

engine distortion and movement, combustionpressures, head movement, variation in boltloading and vibration

These differences in engine design are whysome ROL head gaskets may have a red siliconePozi Seal beading while others will not.

Cylinder Head GasketDesigns

New engine designs and modern materials tech-nology have resulted in considerable changes inhead gasket design. Many new gasket designscan be applied to older engines, so the head gas-ket you install can look different from the gasketbeing replaced. Additionally, there is no one bestdesign since no type or design is best for all appli-cations. Gasket manufacturers engineer the correcthead gasket design for each individual engine.

No-retorque head gaskets

No-retorque head gaskets are now commonand desirable. However, many import applicationsand older domestic engines require the cylinderhead to be retorqued. Retorque-type head gasketstake a set after initial engine operation and relaxto a point where retorquing is needed to restoreproper clamping force. ROLs no-retorque headgaskets are made of modern materials and designtechnologies that have eliminated the set andtherefore the relaxation and loss of clamping force.

On this ROL head gasket for Chrysler 225 in-line six cylinderengines, ROL adds a bead of silicone around the pushrod area foradditional loading in this area of weak clampload.

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The most popular of the early head gasketdesigns was the embossed steel shim gasket. Thisdesign required supplementary sealers for oil andcoolant sealing, but retained torque well. Theproblem with this design is that eventually thecoolant will corrode the steel, leading to gasket fail-ure. Additionally, this type of gasket cannot accom-modate the extreme motion inherent to modernlight weight castings and bi-metal engine designs.With the exception of some performance applica-tions, it is generally accepted that embossed steelshim gaskets are not recommended for replace-ment use.

Modern head gaskets designs fall into threebasic groups:

perforated core composition gaskets

solid core composition gaskets

multi-layered steel (MLS)

ROL perforated core composition gaskets startwith a perforated steel core to which facing layersof either a Kevlar based fiber or high temperaturegraphite material are mechanically clinched.

Combustion armor (firerings) are usuallystamped from cold roll or stainless steel. Thisdesign may also include a silicone coating forcold sealing during engine start up and warm up,and an additional silicone bead around oil andcoolant passages for enhanced fluid sealing. ROL brand perforated core composition gaskets offer

excellent torque retention and generally higher lev-els of conformability and temperature resistance.

Solid core composition type gaskets start with asolid steel core to which either Kevlar or rubberfiber based facings are glued. This type of gasketcan also include silicone coating and beadings.Solid core composition gaskets have a high level oftorque retention but generally lower levels of heatresistance. This is due to the low temperaturerange of facing material binder and laminate(glue) used to bond the facings to the core, and thefact that high temperature facings such as expand-ed graphite are not used because these materialscannot be glued to a solid core. The facing layerson solid core gaskets are generally quite thin andextremely dense which contributes to lower levelsof conformability. While some gasket manufactur-ers continue to use solid core gasket designs, ROLdiscontinued their use many years ago due to poorperformance.

Steel Shim Embossed Gasket

Perforated Core Composition Gasket

Anti-Friction Coating

Steel Fire Ring

Facing

Perforated Steel Core

Facing

Steel Fire Ring

Dense CompositeFacing Material

Glue Solid Steel Core

Solid Core Composition Gasket

Embossing

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Multi-layered steel (MLS) gaskets began inJapan and are now gaining popularity in domesticOEM use as well. MLS gaskets have been shownto reduce bore distortion in the late model, lightweight, siamese bore type (shorter) engines. Themulti-layered steel design features three to sevenmetal layers individually embossed but of differentthickness and with multiple coatings. If a multi-lay-ered steel gasket is to be used, surface finish, wavi-ness, and flatness must be greatly enhance. Theserequirements have been met in engines at the OEMlevel for mass production, however, improved sur-face finishes will be required for other engines notdesigned for use with the MLS gasket.

Intake Manifold Gaskets

The intake manifold gasket insures that no airleaks occur between the intake and the cylinderhead. If there were a leak, the delicate balance ofthe fuel and air mixture would be upset. This gas-ket must perform under high temperatures. If itleaks, it will cause a hot running engine, poor idle,increased NOX pollution, and reduced engineparts life due to detonation. Most intake manifoldgaskets are designed with a steel core. It providesrigidity and prevents wall collapse due to vacuumin intake ports and coolant pressure at water cross-over ports. Rubber and other fibrous materials arebonded (glued or mechanically clinched) to thesteel core to provide a surface seal in contact withthe casting flange faces.

Many V-type engine designs use a manifold gas-ket with an integral splash plate which stops oilsplash on the base of the intake manifold. Thisdesign prevents oil sludge from caking on the hotsection of the manifold which is porting the exhaustcross-over.

Exhaust Manifold Gaskets

Exhaust manifold gaskets help control theexhaust gases leaving the engine through theexhaust manifold. They are subject to extremelyhigh temperatures. Many OEM engines do nothave exhaust gaskets, because the surfaces to besealed are very good and produce no leaks.However, an engine that has been in service forsome time is subjected to thermal warpage and dis-tortion and will require a gasket. The most commontype of exhaust gasket is a perforated steel andfiber gasket with a steel side to the manifold to pre-vent slippage during expansion. ROL steel coregraphite exhaust gaskets are becoming populardue to their superior heat resistance, natural lubric-ity (slipperiness), and torque retention characteristics.

In many cases, there will be embossing around intake ports toachieve a higher sealing pressure.

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Rocker Cover Gaskets

Almost all production rocker covers are a formedmetal design. Flat surfaces with controlled torqueare extremely important. Rocker covers have less fas-teners per inch than any other formed cover. Thecylinder head is not always flat and smooth. The landarea for sealing is narrow and slippage can occur.

There are many materials used for rocker covergaskets. Each has many advantages and disad-vantages. The gasket material must have consider-able compressibility, excellent spring retention,exhibit low creep, and be able to withstand pro-longed exposure to heat. Rubber, cork/rubber,and cork gaskets are widely used. Rubber requiresdifferent installation procedures and cannot beused in conjunction with chemical sealants or adhe-sives.

Oil Pan Gaskets

Oil pan gaskets seal the main oil pan which is either stamped steel or cast metal. The formedmetal pan is the most widely used but has an inher-ent problem. The thin metal of the pan flange is eas-ily drawn and distorted around the bolt holes byover torquing. These flanges must be flat not onlyaround the bolt holes, but also along the length ofthe pan. Metal distortion in this area creates theneed for gasket materials to be thicker and softer.Plain cork and vegetable fiber materials have a ten-dency for oil wicking through the body if the gasketis not fully and uniformly compressed. Cork elas-tomer (cork/rubber blend) materials have reducedwicking substantially and the addition of load lev-elers (steel grommet inserts) at the bolt holesreduces the potential for over tightening. Manylate model applications now use molded rubber oilpan gaskets for improved sealing capability.

Miscellaneous Fibrous Gaskets

Water pump, timing cover, fuel pump, and othermetal assembly gaskets require that power betransmitted through the flange joint either by rotat-ing shaft or lever. Fiber is generally used in thesegaskets because of the high density construction.The flange joint is subjected to the working load.These gaskets keep torque loss to a minimum and

This ROL small block Ford High Temperature exhaust header gas-ket is popular with street performance and race enthusiasts.

These gaskets failed to remain in place. The installer used a siliconesealant during installation which caused the gasket to slip out of position.

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reduce the possibility of bolts vibrating loose andcausing a leak.

Valve Stem Seals

The valve stem seal is a critical element in theefficient operation of an engine. It controls lubri-cation of the valve stem as it slides in the valveguide. Too much oil entering the valve guide resultsin excessive oil consumption. Too little oil causespremature wear on the valve stem and guide.

There are dozens of valve stem seal designs, butthey all fall into two categories: deflector shield(umbrella) and positive guide seals. Deflector sealsactually move up and down with the valve stem act-ing as an umbrella. Positive seals remain fixed onthe valve guide boss, acting as a squeegee on thevalve stem.

Valve stem seals today are required to work atvery high operating temperatures. Temperature isone of the most critical operating conditions for avalve stem seal. Excessive temperatures will causethe seal to harden and become brittle and affect itselasticity and ability to seal and lubricate.

Today valve stem seals are made from threehigh temperature elastomer materials. These areViton, polyacrylic, and nitrile. Nitrile is the most

economical material for valve stem seals howeverViton is widely considered the best materials avail-able due to its superior heat range.

Rear Main Bearing Seals

Rear main bearing seals keep oil from leaking atthe crankshaft around the rear main bearing. Thereare three basic types of seal construction: wick (orrope ) type packing, split (or two piece), and fullradial. Wick, or rope type packings, are commonon many older engines, while split and radial seals,which have a molded synthetic rubber lip, are usedon most newer engines.

Four types of synthetic rubber are commonlyused for rear main bearing seals; nitrile, polyacry-late, silicone, and Viton. Nitrile is used on manyolder applications where heat resistance is not afactor. Polyacrylate is commonly used because it istough and abrasion resistant, with moderate tem-perature resistance to 375 degrees F. Silicone hasa greater temperature range, up to 480 degrees F,but has less resistance to to abrasion and is morefragile than polyacylate. Viton is good for temper-atures up to 450 degrees F and has the abrasionresistance of polyacylate with a temperature rangeapproaching that of silicone. Rear main bearingseals made of the correct material for the applica-tion will always be found in seal sets sold by ROL.

100F

200F

300F

400F

500F

250

375

450HEAT RESISTANCE

NIT

RIL

E

POLY

ACRY

LIC

VITO

N

DEFECTOR SEAL POSITIVE GUIDE SEAL

VALVE STEM SEAL DESIGN

Deflector seals grasp the valve stem, moving up and down with thevalve, shielding the valve guide like an umbrella. The positiveguide seals remain in a fixed position on the valve guide boss, act-ing as a squeegee on the valve stem to control lubrication.

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Coatings, Embossments,and Sealing Beads Coatings

When using mechanical gaskets, one method toimprove the gasket to joint design is the use of coat-ings. These coatings give advantages in sealability,release, flange adhesion, and abrasion resistance.With the use of lighter weight engine designs anddissimilar flange materials, there is greater motion.This motion results in more difficult sealing and pos-sible abrasion of the gasket. Recently, coatingshave been developed that aid in this regard. Thesecoatings contain Teflon, silicone, or graphite andare used to improve the micro sealing of gaskets byflowing into and filling the voids associated with thesurface finish of flanges. These coatings permitflange-to-gasket sliding motion, thus minimizingabrasion of either the gasket or the flange. Thecoatings are also compounded to provideimproved anti-stick characteristics for clean removalfrom the flanges after use. When using coated gas-kets it is imperative that no additional sealers orchemicals be applied as these may react adverse-ly with the chemical composition of the coating andaffect loading of the gasket.

Embossments

Embossing is generally limited to solid metal ormetal reinforced gaskets such as intake andexhaust manifold gaskets. Embossing involvesmetal stamping which produces a raised surfaceheight intended to shift loading to a localized area,such as around the intake manifold ports.

Sealing Beads

The use of elastomeric sealing bead hasincreased dramatically. The most popular elas-tomers in use are either nitrile or silicone. This beadis normally applied by a screen printing processand can be strategically placed to improve thesealing stress at a localized area, such as coolantand oil passages. Bead thickness and width can bevaried depending on clamping pressure andflange conditions.

Since the beads are cured elastomers andbehave like rubber, they dont compress but ratherextrude under load. Most gasket applications aresealed with a bead printed on one side only.

This ROL head gasket for the 350 small block Chevrolet engine uti-lizes a high tech silicone Pozi Seal beading around all oil andcoolant passages.

Steel Core Embossment

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Chemical Sealants

RTV and anaerobics are sealants available prin-cipally in putty-like mastics, tapes, ribbons, andbeads. They have generally not been suitable foruse in the same applications as die-cut or pre-curedgaskets. They are materials that cure in place andthey are capable of forming a permanent sealingmember or gasket between flanges. They areapplied wet to the flanges. The components areassembled and bolted together while the chemicalgasket is wet. Users must be concerned not onlywith cured properties of the material, but with theuncured properties and the chemistry of the curingprocess.

RTV (room temperature vulcanizing) siliconescure by reacting with moisture in the air, thereforethey must be kept tightly sealed just prior to use.RTV silicones require humidity to cure. The moisturein the air reacts with the polymer resulting in a cureto a solid rubber. Cure time corresponds to relativehumidity and thickness required. Curing time isvery long if the relative humidity is below 20%.

Anaerobics cure by the exclusion of air and theacceleration of catalytic effect of an active metalsurface. Cure speed depends on the gap width,type of metal surface being sealed, cleanliness andprior treatment of the metal surface. Anaerobicswill cure on lightly oiled surfaces but cure time willbe affected.

RTV silicones have a high compressibility andextensibility. Anaerobics have little compressibilityand extensibility. RTV silicones are weak materialsin comparison to anaerobics and die-cut gaskets,and should not be considered for high pressureapplications. RTV silicones, while not having out-standing chemical resistance, are resistant enoughfor use against most oils and coolants. Anearobicshave outstanding resistance to oils, coolants, andmany solvents. RTV silicones are considered suit-able for use up to 375 degrees Fahrenheit.

Anaerobics are considered suitable for continuoususe up to 275 degrees Farhrenheit. Both RTV andanaerobics are impermeable to water, coolants,and most oils.

The selection of a mechanical or chemicalgasket depends on a number of factors. Chemicalgaskets are not recommended for the followingapplications:

the temperature is too high or too low for the chemical

the chemicals and medium being sealingare not compatible

thermal and/or mechanical motion is too high for the chemicals

the gasketed joint may have to be pressur-ized before the chemical can cure

the gasket must act as a shim metering orblocking device

the visual appearance of the joint precludes use of chemicals

The most common use of chemical sealants iswhen they are used in conjunction with mechanicalgasket assemblies; sealing the mating line betweengasket sections in intake manifold, oil pan, and rearmain seal applications. The use of RTV silicone asintake manifold end seals has gained in popularityin recent years in both OEM and replacementapplications.

ROL offers replacement gaskets that meet orexceed OE specifications for all popular domesticand import passenger car and light truck applica-tions dating back more than forty years.

The following outlines the materials and designtechnology incorporated into the manufacture ofROL Gaskets.

Cylinder Head GasketsCore - Most ROL cylinder head gaskets uti-

lize a pierced steel core designwhich allows for the use of a widerrange of (and higher temperature)facing materials. On a limited numberof turbocharged diesel applicationsROL uses a solid steel core design.

Combustion Armor - Cylinder head gasketfirerings are constructed of premiumgrade cold roll steel. ROL HighTemperature Head Gaskets (designedfor detonation prone and high com-pression performance engines) havefirerings made from stainless steel.

Facing Materials - On cast iron applications, ROL usesa Dupont Kevlar based fiber materi-al. In order to accommodate theextreme motion inherent to bi-metalengines (cast iron block w/ aluminumheads), ROL extensively uses graphitefacings. Most ROL replacement headgaskets are manufactured to a com-pressed thickness of .038 - .041and will accommodate a .030 -.060overbore. In specific applications ROLmanufactures thicker (than OE) gas-kets for replacement use in order to

accommodate valve clearance prob-lems after machining or to lowercompression. ROL High TemperatureHead Gaskets are manufacturedto .051 compressed thickness.

Coatings - Silicone coatings are added tomany head gaskets to help in coldsealing prior to engine start up andduring engine warm up cycles.

Beadings - Silicone beadings are added toprovide additional loading at areasof low clampforce around oil andcoolant passages.

Future - Increased use of graphite materialsand OE equivalent multi-layered steeldesigns on late model applicationsas required.

Premium Valve Cover and Oil Pan GasketsROL uses premium grade cork/rubber com-

pounds in valve cover and oil pan applications.ROL cork/rubber compounds have a uniform mixof binder and cork granules resulting in a gasketthat insures a good seal but resists shrinkage com-mon to cork gaskets. Most ROL cork/rubber gas-kets are made with a nitrile binder offering a oper-ating temperature range of -20 degrees F to 250degrees F. High temperature applications requiringadditional heat resistance are made with a Viton bin-der which has a temperature range of 450 degrees F.

ROL cork rubber/gaskets are cut to OE specifi-cations for all applications. In performance appli-cations, ROL offers a range of optional thicknessincluding 3/16 and 5/16.

ROL HI-PER BLUE valve cover and oil pan gas-kets are made from a unique cork/rubber blend

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ROL: GASKET DESIGN AND MATERIALS TECHNOLOGY

CHAPTER 2

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that swells 30% upon contact with engine oil atoperating temperature, resulting in a gasket thatincreases sealing pressure as opposed to relaxingover time. This unique blend uses a much higherpercentage of a blue nitrile rubber binder withmuch smaller cork granules resulting in the elimi-nation of wicking of oil past the cork granules, andsuperior torque retention.

ROL molded rubber valve cover and oil pan gas-kets are made to OE specifications from either sili-cone or nitrile rubber as required for the temperaturerange of the application. All locking tabs, beads, andbolt hole grommets are included as per the OEdesign specification.

Seals - Oil and Valve StemROL oil seals and valve stem seals are made

from a variety of materials including nitrile, poly-acralate, silicone, and Viton depending on the appli-cation heat demands and OE specifications. Manyoil seals found in ROL sets are in fact the OE seal.

Intake Manifold Gaskets ROL intake manifold gaskets are designed with a

perforated steel core and asbestos free soft facings(similar to the head gasket material). Additionalloading at intake ports and coolant passages is pro-vided by stamped embossments in the gasket body.This design provides superior strength and maxi-mum confomability over non-cored materials andrubber beadings.

Intake Manifold Valley Pan GasketsStamped from high grade steel to OE specifica-

tions. In applications where motion is a problem,ROL has improved on the OE design with the use ofno-friction teflon coatings and non-asbestos facingslaminated to the intake runner sealing area on boththe head and manifold side.

Exhaust Manifold GasketsDepending on the application, exhaust manifold

gaskets are made in a variety of designsincluding:

Solid stamped steel

Perforated steel on one side with soft (non-asbestos) facing on the opposite side

Perforated steel core with graphite facings(replacement and header gaskets)

Compressed cellulous fiber(header gaskets)

ROL is the only supplier of this unique cork/nitrile blend. Thebest valve cover and oil pan gaskets available today.

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Miscellaneous GasketsAll paper gaskets are completely asbestos free

and made from compressed vegetable fiber ortreated paper meeting OE specifications.

No other engine gasket company makes a gasket strongeror more heat resistant than ROL High Temperature headergaskets.

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SET CONTENTS

Whether you are rebuilding an entire engine orservicing a specific area of the engine only, ROLgasket kits contain all gaskets and seals required tocomplete the assembly. Outlined below are thetypical contents and range of kits offered for a spe-cific application.

HG - Cylinder head gasket only. Packed one perpackage. In applications involving torque-to-yieldhead bolts the bolts are offered separately underan MM prefix and cataloged directly under thehead gasket listing.

HS - Head set. All gaskets and seals required toservice the removal and replacement of the cylinderhead(s). (Sometimes referred to as a valve grind kit.)Typical contents include:

Head gaskets

Valve cover gaskets

Intake manifold gaskets and end seals. RTV silicone if required.

Intake plenum gasket

Exhaust manifold gaskets

Cam plugs (on OHC engines)

Water outlet gaskets

Carburetor or fuel injection mountinggasket

EGR gasket

Distributor mounting gasket

Valve stem seals

Exhaust flange gasket

Air cleaner mounting gasket

FS - Full set. All gaskets and seals required for acomplete engine assembly. In some applicationsROL does not offer a FS full set. Full engine cover-age is obtained by ordering a HS (head set) and aLS (lower set) which together provide completeengine coverage. The intake manifold gasket is notincluded in the FS kit for applications using a valleypan style intake manifold gasket. This gasket mustbe purchased separately.

LS - Lower set. All gaskets and seals required forservicing the lower engine (block).Typical contents include:

Front cover (timing cover) gasket

Water pump gasket

Fuel pump gasket

Oil pump gasket and seals (if required)

Timing cover oil seal

Rear main bearing seal

Oil pan drain plug

Oil pump mounting gasket

Auxiliary shaft seal (if required)

Oil pan gasket and seals.

VS - Valve cover gasket. All gaskets, seals, andplugs required to service the valve or rocker cover.On V-type engines, two valve cover gaskets areincluded. On OHC (overhead cam) and DOHC(dual overhead cam) engines, grommets and semi-circular plugs are included in the VS set. The plugsand grommets are also sold separately under MM(grommets) and VP (semi-circular plugs) prefixesand are cataloged with the valve cover listing.

CHAPTER 3

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Spark plug tube seal sets (where required) arelisted with the valve cover application under a SPprefix.

MS - Intake and exhaust manifold gaskets. Intakeand exhaust manifold kits are cataloged separate-ly, but both have a MS prefix. Typical intake mani-fold kits include intake manifold runner gaskets andend seals (where required), or RTV silicone for usein lieu of rubber or cork end seals. Manifoldplenum gaskets are included in the intake set forfuel injected applications. The manifold plenumgasket is also sold separately and is cataloged withthe intake gasket application as an upper manifoldset.

In-line engines often use a combinedintake/exhaust mounting gasket and is catalogedas a single set, intake & exhaust.

Exhaust manifold gasket sets include all exhaustmanifold mounting gaskets for the entire engineassembly.

OS - Oil pan set. All gaskets and seals required foroil pan replacement. Timing cover shims and oilpan drain plugs are included as required.

TS - Timing cover set. All gaskets required for timingcover replacement.Typical contents include:

Camshaft front oil seal

Timing cover gasket

Fuel pump mounting gasket

Oil pump mounting gasket

Water pump mounting gasket (if required)

Oil pan shim gasket (if required)

Oil pan front seal (if required)

Harmonic balancer wear sleeves are availablefor many engine applications and are catalogedwith the timing cover set with a TC prefix.

RS - Rear main crankshaft bearing oil seal.

WO - Water outlet (thermostat) gasket.

WP - Water pump gasket.

SS - Valve stem seals. Packed 4 per box. Wheredifferent seals are required for intake and exhaustvalves, a notation is made in the appropriate blockin the catalog.

Miscellaneous gaskets: Located after applicationssection.

GB - Automatic transmission pan gaskets.

DS - Axle, differential, and flange gaskets.

CM - Carburetor/fuel injector mounting gaskets.

EG - Exhaust gaskets.

GR - Exhaust recirculation gaskets.

FP - Fuel pump gaskets.

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Most production valve covers are of a formedmetal design. In that valve covers have less fasten-ers per inch than any other formed cover, flat sur-faces with controlled torque are extremely impor-tant. The sealing surface of the cylinder head is notalways flat and smooth, and the land area for seal-ing is very narrow. Additionally, engine vibration cancontribute to a reduction in clamping force over time.

Some late model engines now use valve coversmade of plastic. Over time, these valve covers devel-op serious problems with distortion and warpage,making sealing even more difficult. In manyinstances the ROL replacement gasket has to be bet-ter than the original (production) gasket becausethe sealing demands have changed substantially.

Valve Cover Gaskets

Cork Composition

Originally, valve cover gaskets were made fromcork composition sheets made by grinding corkbark into fine granules bound together with eitherprotein or synthetic resin. Cork sheet gasketsoffered high compressibilty, good crush resistance,negligible side flow, and a high degree of imper-meability, under relatively low clamping loads.Cork sheet gaskets however suffered serious defi-ciencies in relaxation characteristics which con-tributed to a shortened service life. Shelf life andhandling were a problem as well in that the mater-ial dried (and shrank) over time, and was extreme-ly fragile.

Cork Elastomer (Cork/Rubber)

ROL bonds cork granules with various types ofsynthetic rubber to provide a combination typematerial that combines the desirable characteristicsof compressibility and impermeability of cork withthe advantages of synthetic rubber. Advantages ofROL cork/rubber over cork composition materialsare improved handling and shelf life and highertemperature range, together with good resistanceto fluids and less fatigue and relaxation. ROL corkrubber compositions seal internal pressure above50 PSI with a continuous service temperaturerange of -20 degrees F to 250 degrees F.

There are many grades or blends of cork/rub-ber composition and there advantages to using aROL premium or high grade material. Ideally, thecork-rubber blend should be uniform in regard tothe amount of binder compared to the amount andgranule size of cork.

ELIMINATING VALVE COVER LEAKAGE

CHAPTER 4

Many late model valve covers are now designed with a special groove in the valve cover to hold a molded rubber gasket.

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Irregularities in the size and amount of the corkgranules within the cork/rubber blend can lead toleak paths. ROL uses premium cork/rubber blendsand is one of only three manufacturers in NorthAmerica who build, cut, and manufacturer theirown cork/rubber gaskets from start to finish. Mostgasket suppliers buy their gaskets precut, and can-not control the consistency of the blend.Additionally, bargain brands use re-groundcork/rubber extensively, which has a much lowertemperature range and higher susceptibility towicking and fatigue failure, and an overall shorterservice life. When your competitor offers a valvecover gasket at a very low price, check to see if itis a national brand, like ROL, or if it is some no-name gasket.

High temperature can shorten the life of manycork/rubber compounds used for valve cover gas-kets. Because of their physical configuration, someengines place valve cover gaskets unusually closeto sources of high heat. On certain Chrysler bigblocks, for example, exhaust manifolds are only afraction of an inch from the bottom edge of thevalve cover gasket. In high temperature applica-tions such as this, ROL makes cork/rubber gasketswith a Viton binder, which has a sustained heatrange of 450 degrees, giving a margin of safetyagainst heat related failure.

The design characteristics of most cork/rubbergaskets limit their use to temperatures in the rangeof 250 degrees. Additionally, cork/rubber gas-kets, over time, suffer from fatigue and lose springretention, resulting in a relaxation of clamping loadand leakage between the gasket and sealingsurface. This and the capacity for wicking, ormigration, of oil through the material are the majorfactors in some cork/rubber gasket failures.Always specify ROL cork rubber gaskets to insurethe highest quality available.

ROL HI-PER BLUE

Several years ago the engineers at ROL Gasketsdeveloped a new and unique cork/rubber materi-al known as HI-PER BLUE. This blend of materialaddresses the deficiencies inherent in othercork/rubber compounds by eliminating wicking,reducing heat stress, and increasing sealing pressure.

Specifically, ROL has greatly reduced the size ofthe cork granules in the compound which in turneliminated the entrapped air and subsequent wick-ing problems. By the use of a higher temperatureblue nitrile binder ROL has increased the tempera-ture range of cork/rubber gaskets to cover mostvalve cover application heat ranges. The unique characteristic of ROLHI-PER BLUE is thatthe material swells

Premium ROL Cork/Rubber

Bargain Brand Cork/Rubber

Cork Rubber Hi-Per Blue

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to predictable dimensions upon contact withengine oil at operating temperature, which results in agasket that increases sealing pressure throughoutits life, as opposed to succumbing to heat relatedfatigue and relaxation. ROL HI-PER BLUE valvecover gaskets are backed by a limited (to the orig-inal purchaser) lifetime warranty.

Molded Rubber

In response to the sealing demands placed ontodays smaller - hotter running engines, many pro-duction valve cover gaskets are made of syntheticrubber, usually either nitrile or silicone. The advan-tage of rubber is total impermeability (no fluid pen-etration into the gasket material) and a higher oper-ating temperature range (250 degrees - nitrile/375 degrees - silicone). As opposed to cork andcork/rubber, ROL molded rubber gaskets do notcompressed, they extrude under load. Because ofits memory the gasket tries to return to its originalshape and size, pushing against the metal surfacesresulting in a long term seal. Because they extrude(as opposed to compressing), molded rubber gas-kets will shift or move, which required the redesign-ing of valve covers. Generally, valve covers intend-ed for use with molded rubber gaskets aredesigned with a receiver groove or channel thatthe gasket fits tightly into, locking the gasket inplace. In this case, the gasket will be slightly short-er or smaller than the valve cover and is stretchedslightly into place for a secure fit. The bolt holes inmolded rubber gaskets may include a steel grom-met designed to prevent over-tightening and crush-ing or splitting of the gasket. It is not recommend-ed that a cork/rubber gasket be used to replace amolded rubber gasket. Cork/rubber gaskets willnot stretch into place resulting in poor positioning,and they compress rather than deform, resulting inpoor conformability with the sealing surfaces.

Choices When You Need Them

Street performance and race applications placeunique demands on engine sealing and often requirere-engineering of gaskets. ROL recognizes theseneeds and offers a wide range of choices to the per-formance engine builder. For example, ROL offers awide range of valve cover gaskets for popular smallblock and big block performance engines including:

Premium grade cork/rubber 3/16 thick Premium grade cork/rubber 5/16 thick HI-PER BLUE cork/rubber 3/16 thick HI-PER BLUE cork/rubber 5/16 thick Molded nitrile rubber (black) - medium

heat range applications Molded silicone rubber (orange) - high

temperature applications

ROL is a primary supplier of molded rubber parts to the entiregasket industry and offers molded rubber valve cover and oil pangaskets which meet or exceed original equipment specifications forall applications requiring molded rubber.

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Installation Tips

The best way to avoid sealing problems withvalve cover gaskets is to do the job right the firsttime. The following are some of the common con-cerns to address when installing valve cover gaskets.

1. Clean the mating surfaces of all foreign material, however, do not use a degreaser or chemical gasket remover on a plastic valve cover.

2. Inspect the cover for cracks, flaws, and distortion. Distorted bolts holes must be straightened. Distorted cast aluminum and plastics covers are difficult to straighten andshould be replaced.

3. Contact cement can be used to hold the gasket in place during installation with corkand cork/rubber gaskets only. Do not use an adhesive with a molded rubber gasket.

4. Do not use any RTV sealers on any valve cover gaskets. Sealers act as a lubricant and affect the loading on the gasket and may allow the gasket to slip or squeezeout of the flange.

5. Use a properly calibrated torque wrench and follow manufacturers torque specifica-tion. Torque down the cover starting from the center and moving outward in an X pat-tern. Do not over torque as the gasket can split or the valve cover can distort to the point where leakage occurs.

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Whats Detonation?

Detonation (also called spark knock) is bestdescribed as abnormal combustion occurring afterspark ignition.

In the normal combustion process, as the pistonapproaches TDC (top dead center) during the com-

pression stroke, the spark plug fires creating a threephase process of formation, hatching, and propa-gation of a flame front resulting in a controlled burnof the compressed air/fuel mixture through theentire combustion chamber.

PREVENTING HEAD GASKET FAILURECAUSED BY DETONATION

CHAPTER 5

Normal Combustion Process

Detonation

Detonation occurs when excessive heat and pres-sure in the combustion chamber cause the air/fuelmixture to auto-ignite. This produces multiple flamefronts within the combustion chamber instead of acontrolled single flame front. When these multipleflame fronts collide, they do so with explosive force

that produces a sudden rise in cylinder pressureand temperature accompanied by a metallic ping-ing or knocking noise. The violent shock waves cre-ated by detonation subject the head gasket, pis-ton, rings, spark plug, connecting rod, and rodbearings to severe overloading.

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Cylinder Heat and Pressure

In the normal combustion process with the pistonat BDC (bottom dead enter) internal cylinder tem-perature is around 140 degrees with approximate-ly 14.7 psi pressure in the cylinder. At TDC the com-bustion chamber temperature has raised to 840degrees with pressure now in the range of 1000 psi.

When detonation occurs the explosive force of the colliding flame fronts spike cylinder temperaturesbeyond 4500 degrees generating cylinder pres-sures that cannot be accurately measured.Detonation occurring before TDC places tremen-dous stress on the assembly because the piston isstill on its upward stroke and not yet in a positionto utilize the energy being created. Detonationoccurring after TDC results in similar stress becausethe piston is limited in motion by crankshaft travel.

What Causes Detonation?

All fuels have a point where they will self ignite(auto-ignition). Additionally, increasing combustionpressure (compression ratio) causes the combustionchamber temperature to rise, so any factor that rais-es combustion chamber pressure or temperature toa point of self ignition can contribute to detonation.

The major factors known to contribute todetonation include:

Excessive compression ratio A static compression ratio of 9:1 is usually the recommended limit for naturally aspirat-ed engines. Modifications to the original size or configuration of the combustion chamber which reduce the actual volume of the chamber increases the static com-pression ratio. Excessive cylinder head machining, the use of domed pistons, thin-ner head gaskets, and carbon deposits all contribute to detonation by reducing the volume of the combustion chamber.

Over advanced engine timingToo much spark advance can cause cylinderpressure to rise too rapidly resulting in auto-ignition of the air/fuel mixture.

Glow spotsThe edges of dished pistons, sharp points or burrs at the cylinder deck or within the com-bustion chamber, and edges of exhaust valves(particularly if machined) can retain sufficient heat to induce ignition of the air/fuel mixture.

Low octane fuelThe octane rating of a fuel is a means of mea-suring a fuels ability to withstand ignition. Thehigher the octane rating, the more resistant thefuel is to burning. The lower the octane rating,the easier the fuel will ignite.

Lean air/fuel mixtureThere is a point of balance between the amount of fuel and the amount of air in the

This ROL head gasket for the 2.2 / 2.5L Chrysler is made thickerthan OE (stock) to compensate for cylinder head resurfacing.

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combustion fuel mixture where optimum propa-gation of the combustion flame occurs. With alean air/fuel mixture the oxygen content is toohigh and the mixtures ability to resist ignition isseverely decreased. Air leaks in vacuum lines,incorrect carburetor or fuel injection settings, leaking manifold runners, and forced inductionsystems all admit extra air into the engine andlean out the air/fuel mixture.

Incorrect spark plugsThe term heat range refers to the relative tem-perature of the core nose of the spark plug. The words hot or cold spark plugs are often a source of confusion in that normally a hot spark plug is used in a cold (low rpm) engine, and a cold spark plug is used in a hot (high rpm) engine. Use of the proper sparkplug is essential to proper timing and propa-gation of the ignition flame front.

Inefficient cooling system/engine overheating An engine suffering from elevated operating temperatures is more likely to detonate due to the higher combustion chamber tempera-tures. Overheating can be caused by a low coolant fill, slipping fan clutch, too small a fan, too hot a thermostat, a bad water pump, or an inefficient cooling system. Rust and scale deposits in the cooling system can reduce an engines ability to dissipate heat by as much as 60%.

Malfunctioning EGRThe EGR reduces oxides of nitrogen pollution in the exhaust by recirculating small amounts ofexhaust into the intake manifold. Though thegases are hot, they actually have a cooling effect on combustion temperatures by diluting the air/fuel mixture slightly. If the EGR valve isnot functioning, the cooling effect is lost result -ing in higher combustion temperatures under load.

Engine luggingEngine lugging is placing your engine under severe load. When pressing down on the accelerator produces no increase in engine speed the effect is that of forcing more oxygeninto the fuel mixture resulting in a leancondition.

Eliminating Detonation

Eliminating detonation requires that you proper-ly identify the factor(s) contributing to the abnormalcombustion process. In most instances a process ofelimination approach can easily pin point thecause and therefore the cure to detonation. Thesingle most important thing you can do to avoidand eliminate detonation is to maintain the enginein the proper tune with particular attention to sparkplug timing and advance curves. Other factors toemploy would include the following.

Use spark plugs of the correct heat range for the engine

Select fuel of the proper octane rating Maintain the cooling system Retard the timing Chemically remove oil and carbon deposits

from the piston dome and combustion chamber

Avoid a lean air/fuel mixture Intercool forced induction engines Use a thicker head gasket (such as the ROL

HT series) which provides additional sealingstrength while lowering the compression ratio slightly

The Role of the Head Gasket

The role of the head gasket is to seal the com-bustion flame, the hot pressurized engine oil, andthe hot pressurized coolant mixture. Most OE andreplacement gaskets are manufactured to a com-pressed thickness in the range of .038 - .041.

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Traditionally, the head gasket has been theweaker link in the line of components exposed tothe destructive forces of detonation. Recent innova-tions in ROL head gasket materials and designtechnology have vastly improved the overallstrength of the head gasket, and there are now ROLhead gaskets available that will withstand the ex-treme heat and pressures associated with detonation.

The ROL High Temperature Head Gasket

The ROL High Temperature (HT) head gasket ismanufactured to .051 thickness (compressed) andwas designed to fight heat and detonation throughthe use of premium materials and design technology.

Pozi-Seal Beading

Silicone Coating

Stainless SteelFire Ring

Graphite Facing

PerforatedSteel Core

Graphite Facing

Features & Benefits:

Rugged steel core

* Dimensional strength and torque retention

Graphite facing

* Superior heat resistance of 2100 degrees F* Anisotropic, conducts heat laterally to transfer

heat from the engine to the coolant faster andeliminate hot spots

* No binder material to break down at hightemperatures

* Superior conformability to seal minor surface imperfections and machining marks

* Excellent torque retention, even under low torque conditions

* Easy to clean up, doesnt stick to the head orblock so you dont risk gouging the surface scraping off gasket material

* Natural lubricity (slipperiness) to accommodatethe the motion inherent to bi-metal engines (aluminum heads)

Silicone Coating

* Superior cold sealing ability during engine start up and warm up

* No additional sealers or coating required

Pozi-Seal Beading

* Additional loading around critical oil and coolant passages

Stainless Steel Fire Ring

* Additional 200 degrees heat resistance at the combustion seal

.051 Thickness

* Lowers compression ratio slightly* Restores original compression ratio after surface

machining

ROL High Temperature Head Gasketsare available for the following detonationprone engine families:

AMC, Jeep, and Jeep Eagle -151 (2.5L) 4 cyl. & 173 (2.8L) V-6

Chrysler -135 (2.2L) 4 cyl., 153 (2.5L) 4 cyl., 156 (2.6L) 4 cyl., & 181 (3.0L) SOHC

Ford -116 (1.9L) 4 cyl., 351W (5.8L) V-8, 370 (6.2L)V-8, 429 (7.0L) V-8 & 460 (7.5L) V-8

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GM -151 (2.5L) Vin R, all 151 (2.5L) w/crossflow, 151(2.5L) Vin U, 173 (2.8L) V-6, small block 265, 283,302, 307, 327, 350 (5.7L) and big block366, 396,40, 427, 454 Exc. H.D.

Mazda -2.6L (2600cc) Truck

Mitsubishi - 2.6L (2555cc) G54B

ROL High Temperature Head Gaskets arealso available for the following race andstreet performance applications:

AMC -340, 360, 390, & 401

Chrysler -small block 273, 318, 340 & 360 big block - 361, 383, 400, 413, 426 (exc. Hemi) & 440

Ford -small block 260, 289, 302 (5.0L), 351C, 351M,400 big block 352, 390, 406, 427, 428, 429(Exc. Boss) & 460

Chevrolet -small block 262, 267, 283, 302, 305, 307, 327, 350 & 400 big block 396, 402, 427 & 454

Oldsmobile -330, 350, 400, 425, & 455

Pontiac -326, 350, 389, 400 (exc. RAM AIR), 421, 428, & 455 (Exc. H.O.)

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CYLINDER HEAD GASKET INSTALLATION

CHAPTER 6

Installing Cylinder Head Gaskets

The cylinder head gasket forms the most criticalseal on the engine - between the cylinder head andengine block deck. Understanding and employinggeneral installation guidelines can offer addedinsurance that the assembly will be sealed com-pletely and effectively for the service life of theengine. The following are some general guidelinesto the typical head gasket installation.

1. Allow the engine to cool beforedisassembly

Cylinder heads tend to warp if they are removedwhile they are still hot. This is particularly criticalwhen working with aluminum cylinder heads. Heatexpands metal, making assembly bolts more diffi-cult to remove, and more prone to breakage.Additionally, working on a cool engine eliminatesthe risk of burns to the arms, hands, or fingers.

2. Loosen and remove bolts in reverse torque sequence

Follow the manufacturers recommended torquesequence in reverse order to loosen each bolt.Then repeat the process again to remove the bolts.This will minimize the chance that the componentswill warp.

3. Clean mating surfaces of foreign material

All foreign material should be removed from thesealing surfaces. Debris not removed can prevent agood seal. Debris can even damage the block,gasket, and head. On iron components use ascraper and wire brush. Use a non-metallic scraperon aluminum surfaces since they are easily dam-aged. Final cleanup can be accomplished with ageneral degreaser or mineral spirits.

4. Inspect the old head gasket

Inspect the old head gasket for wear and damage.A failed head gasket is often a symptom of the failure,not the cause of the failure, and the old gasket can pro-vide clues to previous as well as potential engine prob-lems. For example, a cracked armor may indicateabnormal combustion (detonation), or a loss or lack ofclampload. Replacing the gasket without correcting theproblem can cause even high quality gaskets to fail again.

Small Block Chevrolet Torque Sequence

1317

16 12

14105

8 4 3 7 11 15

9 1 62

Leakage on this gasket was caused by a badly warpedcylinder head.

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5. Check for warpage and distortion

Place a straight edge lengthwise on the head(and block) surface and slide a feeler gaugebetween the head and the straight edge. Acceptedflatness tolerances for three cylinder applicationsshould not exceed .003 out-of-flat, four cylinderapplications .004 out-of-flat, and six cylinderapplications .006 out-of-flat. Widthwise, all appli-cations should not exceed .002 out-of-flat. Theseare combined specifications for both the head andblock combined and should not exceed the maxi-mum in total.

6. Resurfacing the head

Resurface the head and/or block if out-of-flat-ness exceeds the specifications listed above. Themachine shop should remove just enough metal toreturn the surface to flatness. Excessive resurfacingcan result in possible valve/piston interference,excessive compression ratios, and misalignment ofmanifold bolt holes and ports.

Each time the surface of the head or block ismachined on a V-type engine, the heads arelowered and brought toward the center of theengine. This can result in a misalignment of themanifold bolt holes and ports. One way to correctthis problem is to machine the intake surfaces of thecylinder heads or manifold. This allows the mani-fold to reach a lower position. However, machin-ing of the intake surface also reduces the manifoldend gaps.

The ends of the manifold or block must also bemachined to maintain the original gap size, orcrushing of the end strip seals will occur.

A better solution to a misalignment problem is touse a shim type spacer, or even better, a thickerhead gasket, such as the ROL HT series, to restorecylinder head or block material that has beenmachined away.

7. Inspect all engine parts

Inspect for any irregularities that may causeleaks such as gouges, scratches, or cracks.Replace cracked, scored, or badly warped parts.

8. Never reuse head gaskets

Reusing a head gasket is an open invitation to afailure which can result in engine damage due toloss of coolant and lubricant.

When a new head gasket is installed, it conforms toirregularities on the sealing surface when compressed.

When a gasket is reused, it is impossible to rein-stall it in the same exact position. The compressedmaterial cannot readjust to the irregularities in thesealing surface and failure occurs.

misalignment

before machining

correctalignment

after machining

sealing surface

new gasket conforms tosurface irregularities new gasket

sealing surface

possible leakage paths used gasket

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9. Check head gasket for proper fit

Before installing the new gasket, read all instruc-tions provided with the gasket. Many gaskets arestamped for specific positioning to the front of theengine or for one side of the gasket to be facing thecylinder head. Check the gasket for fit on the headand block, and against the old head gasket.Combustion openings should be slightly larger thanthe engine bore and may have irregular shapes toaccommodate valve pockets in the cylinder head.The gasket coolant holes may be smaller or shapeddifferent from the coolant passages in the head orblock. This is because head gaskets are designedto control or meter coolant flow. There also may beopenings inthe cylinderhead ore n g i n eblock thatare not inthe gasket.These arec a s t i n gholes usedin manufac-turing whichdo not affect operation. The gasket bore size,depending on the engine, usually accommodatesbetween a .040 and .060 overbore. The gasketbore should also accommodate a chamfer of up to.030 cut at 45 degrees.

10. Head and block surface finishes

Check the surface finish with a profilameter. If aprofilameter is not available, use a relatively inex-pensive surface comparator, which is available atmost parts stores. If the casting surface is toosmooth, the gasket cannot grip the surface for adurable combustion seal. If the casting surface istoo rough, the gasket will not completely conformto the surface, causing combustion and fluid leaks.

A micro finish of 90 to 110 RMS (80 to 100 RA)is preferred for composition type gaskets. Latemodel applications using rubber embossed steel ormulti layered steel (MLS) gaskets require a muchsmoother surface finish - 30 RMS (25 RA).

11. Clean and prepare bolts

Wire brush the threads on all assembly bolts.Check the bolt threads for damage. Lightly lubri-cate the threads and underside of each bolt headwith engine oil before assembly. Dry, dirty threadsin poor condition can decrease a bolts clampingforce by as much as 50%. This can lead to falsetorque readings and gasket failure as a result ofinsufficient clampload.

This gasket shows grooving caused by a surface finish that was too rough. The grooving resulted in coolant leakage into the combus-tion chamber and combustion leakage between cylinders.

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12. Check for correct bolt length

If the bolts have stretched or excessive machin-ing has been done, the bolts can hit the bottom ofblind holes. To check for this problem, put a wood-en dowel in the block hole. Mark the hole depthon the dowel and compare this to the length of thebolt threads that go into that hole. If the bolt islonger, it will bottom when in the bolt hole. In thecase where it is determined that the bolt will hit thebottom of the hole, place a hardened steel washerunder the head of the bolt before assembly.

13. Head bolts that penetrate intocoolant passages

Coat bolt threads with a non-hardening sealer ifthey enter the coolant passages. This will eliminatethe potential for coolant seepage around the boltsthreads. Seeping coolant can get into the oil orcause corrosion that can damage engine parts,resulting in failure.

14. Follow the proper torque sequence and torque to specification

Carefully follow the manufacturers recommend-ed torque procedure and torque the head bolts tothe specified torque in foot pounds.

Note: Always make sure that the torque wrenchused is properly calibrated. A mis-calibrated torquewrench will give false torque readings, contributingto failure due to inadequate or inconsistent clam-pload.

If the engine has torque-to-yield bolts, turn thehead bolts the additional amount stated in the man-ufacturers torque specification, still using the prop-er torque sequence.

Note: Do not reuse torque-to-yield (TTY)cylinder head bolts

The torque-to-yield procedure for tighteninghead bolts has led more and more technicians toreplace these bolts rather than reuse them.

The torque-to-yield procedure involves tighteningto a specified torque reading and then adding aspecified partial turn measured in degrees. Thispermanently stretches the bolt and assures a moreuniform clamping force across the cylinder head.Some OE manufacturer specifications allow thereuse of these bolts a specified number of times oras long as they are within certain tolerances.However, technicians usually have no way ofknowing the number of times a bolt has been usedor whether they are stretched beyond safe toler-ances. And, while most OE engine manufacturersdo not say that TTY bolts must be replaced ratherthan reused, they generally recommend it as a wayof preventing problems. ROL offers replacementbolts for all TTY applications.

15. Run the engine after complete reassembly

Check for fluid and combustion leaks.

16. Retorquing the cylinder head gasket

If you used a no-retorque type gasket like thosemanufactured by ROL, your installation job is prob-ably complete. However, gasket manufacturerscannot take into account all engine manufacturerdesign considerations regarding bolt length, thick-ness, and spacing, and therefore there are certainengines that require retorquing. Again, follow themanufacturers torque specification regardingretorquing. Additionally, some head gaskets, espe-cially those manufactured oversees for imports,need to be retorqued. If the gasket design requiresretorquing, run the engine to a normal operatingtemperature (usually 10 to 15 minutes) and shut offthe engine. Carefully retorque the cylinder headbolts for a second time. Retorquing can be donewhile the engine is still warm if the engine is castiron. If the head or block is aluminum, allow theengine to cool to room temperature.

Gasket Definition, Function, & PurposeBasic Operating ConditionsSealed MediumsSurface Characteristics & Clamping LoadsGasket Materials Requirements & PropertiesPurpose & Function of Gasket TypesCoatings, Embossments, & Sealing Bonds

ROL Design & Materials TechnologySet ContentsSealing The Valve CoverValve Cover GasketsChoices When You Need ThemInstallation Tips

Preventing Head Gasket Failure Caused by DetonationWhat is Detonation?Cylinder Heat & PressureWhat Causes Detonation?Eliminating DetonationThe Role of the Head GasketROL High Temperature Head Gaskets

Cylinder Head Gasket Installation