1. Cylinder Heads and Valves

2. Cylinder Heads Purpose – regulates the air/fuel in/out of the engine
Construction
Cast Iron
Cast Aluminum
Overhead valve heads incorporate:
related components
Coolant passages
Valve operation mechanism(s)

3. Cylinder Heads Overhead camshaft heads will also incorporate:
Camshaft(s)
Rocker arms or followers

4. Hemispherical Cylinder Heads
Hemi – a Chrysler term for a symmetrical cylinder design.
Typically valves would be positioned directly opposite in the head with (ideally) a spark-plug positioned between them.
Modern designs my incorporate two spark-plugs.
NOT exclusive to Chrysler!

6. Hemi Head

7. Cylinder Heads
Cross flow head design – the practice of placing the intake port and the exhaust port on opposite sides of the cylinder head.

8. Traditional Arrangement
Traditionally, combustion chambers would have one exhaust valve and one intake valve.

9. Multiple Valves
Four valves per cylinder – two exhaust and two intake valves.
Pentroof design – each pair of valves are inline

10. Intake - Exhaust Ports
The passageways in the cylinder head that lead to/from the combustion area.
Intake:
Larger ports = more airflow
Smaller ports = better velocity for low RPM operation
Longer ports = better atomization on carb and TBI
Shorter ports = denser A/F charge

11. Gasket Matching
Using an intake gasket as a template to “port” the heads

12. Coolant Passages
Coolant travels through the cylinder head from the engine block.
Cylinder head gaskets may be designed to restrict coolant flow rate.
Often a source for corrosion and leakage.

13. Blown Head Gasket

14. Cylinder Head Removal
All aluminum cylinder heads should be removed with a reverse torque procedure.

15. Cylinder Head Resurfacing
Heads should be checked in five places for warpage, distortion, bends or twists.
Check manufacturers specifications, maximum tolerances usually around .004”.

16. Valve Guides
The “bore” in the cylinder head that supports and controls lateral valve movement.
Often integral on cast iron heads
Always an insert on aluminum heads

17. Valve Guides
Steel insert on aluminum heads

18. Valve Stem To Guide Clearance
Always check manufacturers specs
Intake valve will typically be .001 to .003”
Exhaust valve will typically be .002 to .004”
The exhaust valve stem clearance will generally be greater due to the higher operating temperatures.

19. Valve Guide Wear Guides are checked in 3 locations
With a small-hole gauge then measured with a micrometer
Or checked with a small bore gauge

20. Valve Stem Wear
Measured with a micrometer at three separate locations.

21. Valve Stem To Guide Clearance Correction
Oversized Valve Stems – the guide is reamed to accept a larger stem.
Must use a valve with an oversized stem.
Reduced flow rate

22. Valve Stem To Guide Clearance Correction
Valve guide Knurling – a tool is driven into the guide that displaces metal thus reducing the inside diameter of the guide. (p )
The guide is then reamed to attain proper clearance
Not recommended for clearances +.006

23. Valve Stem To Guide Clearance Correction
Valve guide replacement – (insert) the old guide is driven out and a replacement guide is driven in.
The guide may require reaming to achieve proper stem to guide clearance.

24. Valve Stem To Guide Clearance Correction
Valve Guide Inserts – (integral) the old guide is drilled oversized and inserts are installed.
Pressed fit
May be steel or bronze

25. Valve & Seat Service

26. Intake & Exhaust Valves
Automotive valves are of a poppet valve design.

27. Valve Materials Stainless steel May be aluminized to prevent corrosion
Aluminum
Hardened valve tips and faces
Stellite (nickle, chromium and tungsten) valve tips and faces
Stellite is non-magnetic

28. Valve Materials
Sodium-filled – a hollow stem filled with a metallic sodium that turns to liquid when hot (heat dissipation).
Exhaust valves are largely comprised of a chromium material (anti-oxidant) with nickel, manganese and nitrogen added.
May be heat-treated
May be of a two-piece design

29. Intake & Exhaust Valves
Valves are held into place by a retainer and keeper.
Aluminum heads will have a separate spring seat (iron heads will have integral seats)

30. Valve Seats
Integral seats – cast iron heads – induction-hardened to prevent wear
Valve seat inserts – typically aluminum heads – hardened seats are pressed into the heads

31. Valve Inspection Valve tips should not be mushroomed
Most valve damage is due to excessive heat or is debris “forged”.
Replace any valve that appears Burnt
Cracked
Stressed
Necked

32. Valve Springs
A spring “winds-up” as it is compressed – this causes the valve to rotate.
May have inside dampers to control vibration.
Springs are camshaft specific.
Squareness (+ (-) .060)
Spring free height (+ (-) .060)
Compressed force (+ (-) 10%)
Valve open height
Valve closed height

33. Valve Spring Tester

34. Valve Seat Reconditioning
The angle of the valve seat is reconditioned.
Often 3 stage (triple-angle) to promote flow and overhang.
May be done with “seat stones”
May also be done with a SERDI type set-up where the 3 angles are cut with one cutting tip.

35. Valve Reconditioning
The stem is lightly chamfered to insure proper fit in the valve grinder.
The face of the valve is reground using a valve grinder. (45 or 30 degrees typical).
Interference angle – the practice of grinding the face 1degree less than the seat angle.
The valve must retain its “margin” area.
the stem should be ground ½ the value that the face was ground with nonadjustable rockers.

36. Valve Lapping
The use of valve compound and a suction cup stick to establish a pattern
May be done to “freshen” the seat and face areas

37. All compound must be removed prior to service
Valve Lapping
The use of valve compound and a suction cup stick to establish a pattern
May be done to “freshen” the seat and face areas
Also used to check the contact pattern while cutting valve seats
All compound must be removed prior to service

38. Valve Seals
Valve Seals are designed to allow sufficient lubrication of the valve stem/guide and also control oil consumption.
Umbrella seals – hold tightly onto the valve stem
Positive valve stem seals – hold tightly onto the guide
O-rings – controls oil between the spring and retainer

39. Checking Installed Height
If a valve seat and face are cut the valve will sit lower in the head.
The result is that the stem will sit higher on the top of the head.
This will cause the springs to have improper tension.
Installed height is measured and shims are added under the spring to compensate.

40. Camshafts

41. Camshaft The camshaft rotates ½ times the crankshaft – or –
once per four-cycle stroke.
The camshaft may operate the:
Valve train
Mechanical fuel pump
Oil pump
Distributor

42. Camshaft Major function - operate the valve train.
The lobes on the cam open the valves against the pressure of the valve springs.
Bearing journal can be internally or externally lubricated (oiled).

43. When installing externally oiled cam bearings it is essential that the holes in the bearings lineup with the oil passages in the block

44. Camshaft Pushrod engines have the cam located in the block.
Cam is supported by the block and the cam bearings.

45. Camshaft Cam may or may not be held in place by a thrust plate.
Most roller camshafts are held in by a thrust plate.

46. Overhead Camshafts
Overhead camshafts are either belt or chain driven and are located in the cylinder heads.

47. Overhead Camshafts Will use one of the following: Cam followers
Rocker arms
May have a one piece lifter – rocker design
A bucket design

48. Camshaft Operation

49. Bucket Design

50. Camshaft Followers

51. Rocker Arms

52. Design A cam casting will include Lobes Bearing journals
Drive flange (gear)

53. Design A cam casting may include Oil pump drive gear(s)
Fuel pump eccentric (mechanical fuel pump)

55. This designation is actually determined by the lifter design.
Classification
Camshafts are of one of four types:
Hydraulic flat-tappet
Hydraulic roller
Solid flat-tappet
Solid roller
This designation is actually determined by the lifter design.

56. Hydraulic flat-tappet
The lifter is “spring” and oil loaded to allow for compensation.
Traditional O.E. style (1950’s – mid 90’s)
Used with flat or convex-faced lifters
Generally cast iron or hardened steel
Requires a “break-in” period to establish a wear pattern

58. Flat tappet Lifters

59. Hydraulic flat-tappet
Most cams are coated at the factory with manganese phosphate . This gives the cam a dull black appearance. This coating is to absorb and hold oil during the “break-in period”.
                         

60. Hydraulic flat-tappet
Most late model designs use a convex bottom (.002”) to encourage lifter rotation.
This rotation helps reduce lifter and (or) bore wear.
The Cam lobe will also be slightly tapered (.0007” ”).
This provides for a wider contact pattern.

61. Hydraulic flat-tappet
Camshaft “break-in”
The lobes of the cam and the bottom of the lifters must be coated with a molydisulfide lubricant often called “cam lube”.
This insures that the cam is properly lubricated during “break-in”.

63. Hydraulic flat-tappet
Camshaft “break-in”
Typical procedure –
Maintain 1,500 RPM for minutes
Drain the engine oil a immediately afterwards
Check the recommended procedure and lube for your particular cam!

64. Hydraulic Roller
The lifter is “spring” and oil loaded to allow for compensation.
The contact between the cam and lifters are separated by a steel roller.
This roller reduces friction.
Lifters cannot be allowed to rotate within the lifter bore.

65. Hydraulic Roller
A roller camshaft is generally made of non-hardened steel.
The lobes must be “finished” by the manufacturer prior to assembly
there is no “break-in period”.

66. Hydraulic Lifters (tappets)
Hollow cylinders fitted with a plunger, check valve, spring and push-rod seat.

67. Hydraulic Lifters (tappets)

68. Hydraulic Lifters
The oil passed through the check valve exits through the hole in the push rod seat.
The oil then passes through the pushrod to lubricate the rocker arms.

69. Engine oil pressure forces oil into the lifter through the oil inlet holes.
A check valve and ball hold most of the oil inside the lifter “hydro-locking” the plunger inside the cylinder.

70. Hydraulic Lifter Preload
Also called valve lash.
The distance between the pushrod seat and snap-ring when the lifter is resting on its base circle.
Typical values range from .020 to .045”.
Check manufacturers specifications.

72. Hydraulic Lifter Preload
Adjusted by:
Adjustable rocker arms
Often referenced by “turns past zero lash”
Non-adjustable rocker arms
Longer or shorter pushrods
Shim or grind rocker stands

73. Hydraulic Lifter Preload
Necessary if:
Cylinder head has been decked
Cam has been changed
Altered head gaskets
Camshaft is worn
An engine rebuild

74. Hydraulic Lifter Valve-float NOT GOOD
The lifter fills with oil faster than it can purge it. This raises the lift of the camshaft.
Usually caused by excessive RPM.
May damage valves, pushrods, pistons etc.

75. Solid Flat-tappet and Roller
No internal hydraulic absorption.
Allows for a more consistent valve lift, especially at high RPM.
Noisy when cold, more frequent and precise valve-lash adjustments required.

76. Solid Flat-tappet and Roller
Oil is diverted through the pushrods via a pushrod seat.

77. Solid Flat-tappet and Roller
No lifter preload – valve lash only.
Lash values may be given hot or cold
Typical values range from ”.

78. Cam Specifications Lift Duration Valve overlap
Lobe center (separation angle or lobe spread)

79. As lift increases the forces on the entire valve train also increase.
Lobe Lift
The amount the cam lobe lifts the lifter
Expressed in decimal inches
As lift increases the forces on the entire valve train also increase.

82. Lobe Lift
Asymmetrical design – the amount of lift between the intake and exhaust lobes is different.
Symmetrical design - the amount of lift between the intake and exhaust lobes is the same.

83. Duration
The number of degrees of crankshaft rotation for which the valve is lifted off of the seat.
If the amount of degrees that the intake and exhaust valve are open differ – it is of an asymmetrical design.

84. Usually expressed as one of two values
Duration
Usually expressed as one of two values
Duration (at zero lash)
Duration at .050” lift – preferred method
Compensates for tappet styles and clearances

85. Duration More duration = rougher idle and better high RPM performance
Less duration = smoother idle and better low RPM performance

86. Valve Overlap
The number of degrees of crankshaft rotation that both valves are off of their seat (between the exhaust and intake strokes).
Lower overlap = a smoother idle and better low RPM operation
Higher overlap = better high RPM operation

87. Valve Overlap
Having the exhaust valve still open when the intake starts to open uses the exhaust "pull" out the exhaust port to help start the intake charge entering the chamber -- before the piston has started down and has generated it's own vacuum.

88. Lobe Separation Angle
The difference, in degrees, between the center of the intake lobe and the center of the exhaust valve.
The smaller the angle the greater the valve overlap
The larger the angle the less the overlap
Link to LSA effects

89. Camshaft (Valve) Timing
Pushrod- Type Engine
It is crucial that the crankshaft, camshaft and balancing shaft (if equipped) are timed correctly.
This is often achieved by aligning “timing marks” on the gears

90. Camshaft (Valve) Timing
V-type DOHC Design
Modern DOHC motors may incorporate chains and belts on the same motor
Some of these designs are quite elaborate

91. Camshaft (Valve) Timing
Some designs do not provide “alignment marks” and require special tools for proper timing

92. Camshaft Degreeing Advanced cam timing Retarded timing
The camshaft is slightly ahead of the crankshaft
More low speed torque
less high RPM power
Retarded timing
– The camshaft is slightly behind the crankshaft
More high RPM power
Reduced low RPM torque

94. Adjustable Camshaft Gear