2CYLINDER HEAD CONSTRUCTION Valve guide constructionValve seat constructionDiesel pre-chamber cupStratified charge chamber
3Types of Cylinder Heads Old fashion FlatheadsOverhead Valve (OHV or I-Head)Single Overhead Cam (SOHC)Dual Overhead Cam (DOHC or Twin cam)
4Flathead 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.
6VALVE TRAIN CONSTRUCTION Valve constructionValve seal constructionValve spring constructionValve spring shimValve retainers and keepersValve spring seatValve rotatorsValve stem cap
7Valve Train Components Valve train components will vary depending on the type of head configuration.OHV, SOHC or DOHC
8Overhead 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.
9Single 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.
10Dual 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.
12Camshafts 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.
13CAMSHAFT CONSTRUCTION Cam lobesCamshaft thrust plateCam bearingsCam housing and cam cover
14Cam 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.
15Cam Lobe Lift The distance the valve is pushed open. It is determined by the height of the lobe.
16Cam 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!
17Camshaft 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.
18Gear to Gear Drive Simplest drive system. Reliable and strong but noisy.Reverses Direction of Power 2 timesCW>CCW>CW
19Gear and Chain Drive Quieter the gear types. Allows cam to be further away from crankshaft.
20Timing 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.
21Installing 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.