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ENGINE TOP END

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CYLINDER HEAD CONSTRUCTION

Valve guide construction

Valve seat construction

Diesel pre-chamber cup

Stratified charge chamber

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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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Flathead EnginesAll 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.

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VALVE TRAIN

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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

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Valve Train Components

Valve train components will vary depending on the type of head configuration.

OHV, SOHC or DOHC

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Overhead Valve EnginesHas valves in cylinder head increasing compression.

Camshaft still in block.

Uses lifters, pushrods and rocker arms.

Most common head design until 1990’s.

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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.

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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.

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DOHC

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CamshaftsOpens 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.

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CAMSHAFT CONSTRUCTION

Cam lobes

Camshaft thrust plate

Cam bearings

Cam housing and cam cover

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Cam Lobe TerminologyHeel 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.

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Cam Lobe LiftThe distance the valve is pushed open.

It is determined by the height of the lobe.

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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!

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Camshaft DrivesGear on gearGear and chainBelt and notched pulleyCam gear ALWAYS is twice as large as the crank gear, this makes the cam turn

at ½ the

speed of the crank.

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Gear to Gear Drive

Simplest drive system.

Reliable and strong but noisy.

Reverses Direction of Power 2 times

CW>CCW>CW

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Gear and Chain Drive

Quieter the gear types.

Allows cam to be further away from crankshaft.

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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.

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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.

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OHC

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OHC direct

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OHC intermittent Shaft

Intermittent Shaft drives distributor

Must Align ALL (3) Timing marks!

Belt tension pulley

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Timing Variations

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VALVE &CAMSHAFT PLACEMENT

OHC / SOHC

OHV

DOHC

In Block I T

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VALVE OPERATION

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

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VALVE LIFTERS

Solid Lifters

Roller Lifters

Hydraulic Lifters

Followers

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SOLID LIFTERS

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ROLLER LIFTERS

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HYDRAULIC LIFTERS

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FOLLOWERSohc

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Valve Lifter Terminology

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Valve Lifters

Also known as cam followers or tappets.

Come in three types: Come in three types: ********

Mechanical or solid.

Hydraulic.

Roller (which can be hydraulic or solid).

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PUSH ROD CONSTRUCTION

Hollow tube

Steel

Vary in length

Fit between Lifter and rocker arm

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PushrodsMetal rod which transfers force from the lifter to the rocker arm.

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ROCKER ARM CONSTRUCTION

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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.

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Rocker ArmsRoller- Stamped

Stamped

CastAdjuster

Pivot

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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.

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Valve Overlap

This is when the intake and exhaust valve are open at the same time.

It doesn’t seem right but it works.

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INTAKE MANIFOLDCONSTRUCTION

Variable induction system

                                                                                                 

           

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EXHAUST MANIFOLD CONSTRUCTION

Single Exhaust

Dual Exhaust

Single w/crossover

Headers