1. Modern Automotive Technology PowerPoint for by Russell Krick
Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

2. Chapter 13
Engine Top End
Construction

3. Contents Cylinder head construction Valve train construction
Intake manifold construction
Exhaust manifold construction

4. Engine Top End
Includes the cylinder head, valve train, valve cover, and intake and exhaust manifolds

5. Cylinder Head Construction
A bare cylinder head is a head casting with all of its parts removed
If a cylinder head becomes damaged, the technician may need to install a new bare head
All the old, reusable parts can be removed and installed in the new head

6. Cylinder Head and Parts

7. Cylinder Head Construction
This cast aluminum head has four-valve combustion chambers

8. Cylinder Head Construction
This cast iron head has two-valve combustion chambers

9. Valve Guide Construction
There are two basic types of valve guides:
integral valve guides
pressed-in valve guides

10. Integral Valve Guide Part of the cylinder head casting
Simply a hole machined through the cylinder head
Very common because of its low production cost

11. Pressed-In Valve Guide
Separate sleeve forced into a hole machined in the cylinder head
Made of cast iron or bronze
During repair, a worn guide can be pressed out and a new guide can be quickly pressed in

12. Valve Seat Construction
Valve seats can be integral or pressed-in
Integral valve seat
machined portion of the cylinder head casting
Pressed-in valve seat
separate part that is forced into a recess cut into the head
commonly used in aluminum heads

13. Valve Seats and Guides

14. Valve Seat Angle Angle formed by the face of the seat
Most engines use a 45º angle
Some high-performance engines use seat angles of 30º

15. An interference angle increases sealing pressure and speeds seating
Valve Seat Angle
An interference angle increases sealing pressure and speeds seating

16. Diesel Prechamber Cup
Pressed into the cylinder head of some diesel engines
Holes are machined into the deck
Prechambers are force-fit into these holes
Each prechamber forms an enclosure around the tip of an injector and glow plug

17. Area is heated by the glow plug for better cold starting
Diesel Prechamber Cup
Area is heated by the glow plug for better cold starting

18. Stratified Charge Chamber
Fits into the cylinder head casting to form an auxiliary chamber
Uses a rich fuel mixture in the auxiliary chamber to ignite a lean mixture in the main combustion chamber

19. Stratified Charge Chamber

20. Valve Train Construction
The valve train controls the opening and closing of the cylinder head ports
Construction will vary with engine design
To be able to work on any type of valve train, you must understand these differences

21. Valve Construction Automotive engines commonly use poppet valves
Some valve stems are chrome plated to better resist wear
Grooves are cut into the valve stem tops for the keepers

22. Valve Construction A. Polished intake valve B. Stock exhaust valve
C. Hollow exhaust valve is filled with sodium for cooling

23. Valve Face Angle Angle formed between the valve face and valve head
Normal valve face angles are 45º and 30º

24. Sodium-Filled Valves Used when extra valve cooling action is needed
During operation, the sodium inside the hollow valve melts, becoming a liquid
This liquid is used to cool the valve

25. Sodium-Filled Valves
When the valve is opened, the sodium splashes down into the head and collects heat
When the valve is closed, the sodium splashes up into the stem
Heat transfers out of the sodium and into the stem, valve guide, and engine coolant

26. Stellite Valve
Stellite coating on its face retards wear and allows the use of unleaded gasoline

27. Valve Seal Construction
Valve seals come in two basic types:
umbrella valve seals
O-ring valve seals

28. Umbrella Valve Seal Shaped like a cup
Made of neoprene rubber or plastic
Slides down over the valve stem before the spring and retainer
Covers the small clearance between the valve stem and guide
Keeps oil from being drawn into the cylinder head port and combustion chamber

29. Umbrella Valve Seal
A. Synthetic rubber seal with plastic shedder insert
B. All synthetic rubber seal
C. Plastic valve seal

30. O-Ring Valve Seal
Small round seal that fits into an extra groove cut in the valve stem
Seals the gap between the retainer and valve stem
Stops oil from flowing through the retainer, down the stem, and into the guide
Fits onto the valve stem after the spring and retainer

31. O-Ring Valve Seal

32. Used to limit the amount of oil that splashes on the valve stem
Nylon Shedder
Used to limit the amount of oil that splashes on the valve stem

33. Valve Spring Construction
This dual coil spring is designed to increase spring pressure

34. Valve Spring Terminology
Spring tension
stiffness of a valve spring
service manual will give the tension in pounds or kilograms for specific compressed lengths
Spring free length
length of the spring when removed from the engine

35. Valve Spring Shim
Very thin, accurately machined washer used to increase spring tension
When a shim is placed under a spring, the open and closed lengths of the spring are reduced
Provides a means of restoring full spring pressure without spring replacement

36. Valve Retainers and Keepers
Used to lock the valve spring onto the valve

37. Valve Spring Seat
Cup-shaped washer installed between the cylinder head and the bottom of the valve spring
Provides a pocket to hold the bottom of the valve spring

38. Valve Rotators
Turn the valves to prevent carbon buildup and hot spots on the valve faces
May be located under or on top of the valve spring
Commonly used on exhaust valves, which are exposed to more heat than intake valves

39. This engine uses a valve rotator for each exhaust valve
Valve Rotators
This engine uses a valve rotator for each exhaust valve

40. This engine uses a valve rotator for each valve
Valve Rotators
This engine uses a valve rotator for each valve

41. Valve Stem Cap May be placed over the end of the valve stem
Helps prevent stem and rocker arm wear
Free to turn on the valve stem
Serves as a bearing that reduces friction
May be used to adjust clearance in the valve train

42. Camshaft Controls when the valves open and close
May be driven by gears, a chain, or a belt
There may be one or two camshafts per cylinder head

43. Camshaft
In dual overhead cam engines, there are two camshafts per cylinder head

44. Cam Lobes Precision-machined and polished surfaces on the camshaft
Variations in lobe shape control:
when each valve opens in relation to piston position
how long each valve stays open
how far each valve opens

45. Cam Lobe

46. Camshaft Terminology Camshaft lift Camshaft duration Valve timing
how far the valve opens
Camshaft duration
how long the valve stays open
Valve timing
valve opening and closing in relation to the position of the pistons

47. Camshaft Terminology Variable valve timing Valve overlap
engine can alter when the valves open with engine speed
Valve overlap
time when both the intake and exhaust valves in the same cylinder are open
used to improve the movement of gases through the engine

48. Valve Timing

49. Dual Cam Lobes
Some camshafts are machined with dual cam lobes that have two different profile shapes
one lobe is designed for low-speed efficiency while the other lobe is designed for high-speed efficiency
The ECM operates a solenoid valve that controls oil flow to shift the rocker arms from one lobe profile to the other

50. Hollow Camshafts Have their lobes pressed onto the shaft
To lock the lobes in place, an oversize steel ball is forced down through the center of the hollow shaft
Produces a lightweight camshaft

51. Camshaft Thrust Plate Used to limit camshaft end play
Bolts to the front of the block or cylinder head
When the drive gear or sprocket is bolted in place, the thrust plate sets up a predetermined camshaft end play

52. Cam Bearings
One- or two-piece inserts that are installed in the block or cylinder head

53. Cam Housing and Cover Cam housing Cam cover
casting that bolts to the top of the cylinder head to hold the camshaft
used in some overhead cam engines
Cam cover
lid over the top of the cam housing
prevents valve train oil spray from leaking out of the engine

54. Valve Lifters
Ride on the camshaft lobes and transfer motion to the other parts of the valve train

55. Operate quietly by maintaining zero valve clearance
Hydraulic Lifters
Operate quietly by maintaining zero valve clearance

56. Hydraulic Lifters
The lifter adjusts automatically with temperature changes and part wear

57. Hydraulic Lifter Operation
Charging cycle
when the valve closes, oil rushes into the lifter, pushing up on the internal disc or plunger to maintain zero clearance
Leak-down cycle
when the cam acts on the lifter, oil is trapped in the lifter by a check valve
lifter acts as a solid unit to push the valve open

58. Hydraulic Lifter Operation

59. Transfer cam lobe action to the push rod
Mechanical Lifters
Transfer cam lobe action to the push rod

60. Mechanical Lifters Do not contain oil Periodic adjustment is required
Adjustment is normally provided at the rocker arm
Small valve train clearance needed causes clattering or clicking noise when the valves open and close

61. A small roller rides on the camshaft lobe to reduce friction
Roller Lifters
A small roller rides on the camshaft lobe to reduce friction

62. Fits between the camshaft and valve
OHC Follower
Fits between the camshaft and valve

63. OHC Follower Components

64. Push Rods Metal tubes or rods with specially formed ends
Used in cam-in-block engines to transfer motion from the lifters to the rocker arms

65. An inline engine using a pivot ball to hold the rocker arm
Push Rods
An inline engine using a pivot ball to hold the rocker arm

66. Used to limit side movement of the push rods
Push Rod Guide Plates
Used to limit side movement of the push rods

67. Transfer valve train motion to the valve stem tips
Rocker Arms
Transfer valve train motion to the valve stem tips

68. Used to hold the rocker arm in place over the valve
Pivot Balls (Stands)
Used to hold the rocker arm in place over the valve

69. Adjustable Rocker Arms
Used to change the valve train clearance
Either a screw is provided on the rocker arm or the rocker arm pivot point can be changed
Must be used with mechanical lifters

70. Nonadjustable Rocker Arms
Have no means of changing valve clearance
Used only with some hydraulic lifters
The rocker arm assembly is tightened to a specified torque
presets the lifter plunger halfway in its travel
Push rod length can be changed for clearance adjustments

71. Intake Manifold
Construction

72. Intake Manifold
Holds the throttle body and has passages, called runners, going to each cylinder head port
May contain water jackets for cooling
Cast of iron, aluminum, or plastic

73. Manifold Runners
Carry either the air-fuel mixture or air to the cylinder head ports
Exhaust passages warm the manifold

74. “Ram Manifold” Assembly
Takes the place of a traditional intake manifold

75. Composite Manifolds
Intake manifolds can be made of glass-filled nylon or plastic
Weighs half as much as aluminum
Plastic runners are smoother than metal on the inside, improving airflow
Brass thread inserts are molded into the plastic, allowing parts to be bolted to the manifold

76. Flame Arrester
Located between the air filter and the engine intake manifold
Prevents backfire damage to the air filter
Made of metal mesh to prevent the flame of a backfire from entering the air filter housing

77. Variable Induction System
Provides increased engine efficiency and performance
Uses two sets of intake runners controlled by butterfly valves
Butterfly valves are computer-controlled

78. Variable Induction System
At low engine speeds, the system uses the longer intake runners, improving low-end torque
When a specific engine speed is reached, the computer opens the butterfly valves over the shorter intake runners
Airflow is increased for added power

79. Exhaust Manifold
Construction

80. Exhaust Manifold
Routes burned exhaust gases from the cylinder head exhaust port to the exhaust pipe
Made of cast iron or steel tubing

81. Intake and exhaust manifolds with their related components