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ENGINE TOP END

ENGINE TOP END. CYLINDER HEAD CONSTRUCTION. Valve guide construction Valve seat construction Diesel pre-chamber cup Stratified charge chamber. Types of Cylinder Heads. Old fashion Flatheads Overhead Valve (OHV or I-Head) Single Overhead Cam (SOHC) Dual Overhead Cam (DOHC or Twin cam).

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ENGINE TOP END

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  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 http://www.howstuffworks.com/engine-cam.htm

  28. VALVE LIFTERS • Solid Lifters • Roller Lifters • Hydraulic Lifters • Followers

  29. SOLID LIFTERS

  30. ROLLER LIFTERS

  31. HYDRAULIC LIFTERS

  32. FOLLOWERSohc

  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 MANIFOLDCONSTRUCTION • Variable induction system

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

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