1. ENGINE TOP END

2. CYLINDER HEAD CONSTRUCTION
Valve guide construction
Valve seat construction
Diesel pre-chamber cup
Stratified charge chamber

3. Types of Cylinder Heads
Old fashion Flatheads
Overhead Valve (OHV or I-Head)
Single Overhead Cam (SOHC)
Dual Overhead Cam (DOHC or Twin cam)

4. Flathead Engines All valve train parts are in the cylinder block.
Cylinder heads have nothing more than water jackets, spark plug threaded hole and some bolt holes.
Tend to be very low compression. Poor power by today’s standards.

5. VALVE TRAIN

6. VALVE TRAIN CONSTRUCTION
Valve construction
Valve seal construction
Valve spring construction
Valve spring shim
Valve retainers and keepers
Valve spring seat
Valve rotators
Valve stem cap

7. Valve Train Components
Valve train components will vary depending on the type of head configuration.
OHV, SOHC or DOHC

8. Overhead Valve Engines
Has valves in cylinder head increasing compression.
Camshaft still in block.
Uses lifters, pushrods and rocker arms.
Most common head design until 1990’s.

9. Single Overhead Cam (OHC)/(SOHC)
Single cam mounted in head.
Opens both intake and exhaust valves.
One cam on an inline engine and two cams on a vee engine.

10. Dual Overhead Cam (DOHC)
Camshafts mounted in cylinder head.
One cam opens intake valves and one opens exhaust valves.
Often used with 4 valves per cylinder.
Most high performance of all types.
Vee engines have 4 cams.

11. DOHC

12. Camshafts Opens the valves at the right time.
Actually converts rotary motion to reciprocating motion.
Uses a cam lobe for each valve.
Usually made of cast iron.
Has a great effect on engine performance.
Can be given auxiliary functions like running the oil pump or distributor.

13. CAMSHAFT CONSTRUCTION
Cam lobes
Camshaft thrust plate
Cam bearings
Cam housing and cam cover

14. Cam Lobe Terminology Heel as known as the base circle.
Nose is the tip of the lobe which determines cam lift.
Opening and closing flanks and ramps.
Timing points are where the cam starts to open and close the valve.

15. Cam Lobe Lift The distance the valve is pushed open.
It is determined by the height of the lobe.

16. Cam Duration This chart is in degrees of crankshaft rotation.
Note when the valves open and close and on which strokes. This is the duration.
It’s not what it may seem to be!

17. Camshaft Drives Gear on gear Gear and chain Belt and notched pulley
Cam gear ALWAYS is twice as large as the crank gear, this makes the cam turn at ½ the speed of the crank.

18. Gear to Gear Drive Simplest drive system.
Reliable and strong but noisy.
Reverses Direction of Power 2 times
CW>CCW>CW

19. Gear and Chain Drive Quieter the gear types.
Allows cam to be further away from crankshaft.

20. Timing Belt Used primarily on overhead cam engines.
Uses a kevlar belt.
(police vests)
Can snap or stretch causing catastrophic damage to non-free running engines.
Chains remain more popular with engine makers.

21. Installing Timing Chains
Look for the timing marks on the gears.
Point the marks at each other 6 and 12 o’clock.
Install cam gear to camshaft.

22. OHC

23. OHC direct

24. OHC intermittent Shaft
Intermittent Shaft drives distributor
Must Align ALL (3) Timing marks!
Belt tension pulley

25. Timing Variations

26. VALVE &CAMSHAFT PLACEMENT
OHC / SOHC
OHV
DOHC
In Block I T

27. VALVE OPERATION

28. VALVE LIFTERS
Solid Lifters
Roller Lifters
Hydraulic Lifters
Followers

29. SOLID LIFTERS

30. ROLLER LIFTERS

31. HYDRAULIC LIFTERS

32. FOLLOWERS ohc

33. Valve Lifter Terminology

34. Valve Lifters Also known as cam followers or tappets.
Come in three types: ****
Mechanical or solid.
Hydraulic.
Roller (which can be hydraulic or solid).

35. PUSH ROD CONSTRUCTION Hollow tube Steel Vary in length
Fit between Lifter and rocker arm

36. Pushrods
Metal rod which transfers force from the lifter to the rocker arm.

37. ROCKER ARM CONSTRUCTION

38. Rocker Arms
Rocker arms are made of stamped steel, cast iron or aluminum.
They transmit the force of the pushrod to the valve.
Some have adjusters.

39. Rocker Arms
Roller- Stamped
Adjuster
Cast
Pivot
Stamped

40. Valves Called mushroom or poppet valves. Made of high quality steel.
The exhaust valve has one of the toughest jobs in the engine having to withstand temperatures of 1300 degrees F.

41. Valve Overlap
This is when the intake and exhaust valve are open at the same time.
It doesn’t seem right but it works.

42. INTAKE MANIFOLD CONSTRUCTION
Variable induction system
                                                                                                            

43. EXHAUST MANIFOLD CONSTRUCTION
Single Exhaust
Dual Exhaust
Single w/crossover
Headers