Engine component

7/29/2019 Engine component

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ENGINE TOP END


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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 nothingmore than water jackets,spark plug threaded hole andsome bolt holes.

Tend to be very lowcompression. Poor power bytodays standards.


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VALVE TRAIN


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VALVE TRAIN

CONSTRUCTIONValve construction

Valve seal construction

Valve spring construction

Valve spring shim

Valve retainers and keepers

Valve spring seatValve rotators

Valve stem cap


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Valve Train Components

Valve train

components will

vary depending onthe 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 1990s.


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Single Overhead Cam

(OHC)/(SOHC)Single cam mountedin head.

Opens both intake

and exhaust valves.

One cam on an

inline engine and

two cams on a veeengine.


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Dual Overhead Cam (DOHC)

Camshafts mounted incylinder head.

One cam opens intakevalves and one opens

exhaust valves.Often used with 4valves per cylinder.

Most high performanceof all types.

Vee engines have 4cams.


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DOHC


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Camshafts

Opens the valves at the

right time.Actually converts rotarymotion to reciprocatingmotion.

Uses a cam lobe for eachvalve.

Usually made of cast iron.

Has a great effect on

engine performance.Can be given auxiliaryfunctions like running theoil pump or distributor.


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CAMSHAFT

CONSTRUCTIONCam lobes

Camshaft thrust

plateCam 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 andramps.

Timing points are

where the cam

starts to open andclose the valve.


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Cam Lobe LiftThe distance thevalve is pushed

open.

It is determined bythe height of the

lobe.


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Cam Duration

This chart is indegrees ofcrankshaft rotation.

Note when the

valves open andclose and on whichstrokes. This is theduration.

Its not what it mayseem to be!


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Camshaft DrivesGear on gear

Gear and chainBelt and notchedpulley

Cam gear ALWAYS

is twice as large asthe crank gear, thismakes the cam turn

at thespeed of the crank.


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Gear to Gear Drive

Simplest drive

system.

Reliable and strongbut 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 befurther away from

crankshaft.


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Timing Belt

Used primarily onoverhead cam engines.

Uses a kevlar belt. (police vests)

Can snap or stretchcausing catastrophicdamage to non-freerunning engines.

Chains remain morepopular with enginemakers.


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Installing Timing Chains

Look for the timing

marks on the gears.

Point the marks ateach other 6 and 12

oclock.

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

PLACEMENTOHC / SOHCOHV

DOHC

In Block

I

T

VALVE OPERATION


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VALVE OPERATION

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


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VALVE LIFTERS

Solid Lifters

Roller Lifters

Hydraulic LiftersFollowers


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SOLID LIFTERS


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ROLLER LIFTERS

HYDRAULIC LIFTERS


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HYDRAULIC LIFTERS

FOLLOWERS


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FOLLOWERS

ohc

V l Lift T i l


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Valve Lifter Terminology


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Valve Lifters

Also known as cam

followers or tappets.

Come in threetypes: ****

Mechanical or solid.

Hydraulic.

Roller (which can be

hydraulic or solid).


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PUSH ROD

CONSTRUCTIONHollow tube

Steel

Vary in lengthFit between Lifter

and rocker arm


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PushrodsMetal rod which transfers force from the lifter to the

rocker arm.

ROCKER ARM


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ROCKER ARM

CONSTRUCTION

Rocker Arms


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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.

Rocker Arms


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Rocker ArmsRoller- Stamped

Stamped

CastAdjuster

Pivot

V l


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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 temperaturesof 1300 degrees F.

Valve Overlap


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Valve Overlap

This is when the

intake and exhaust

valve are open atthe same time.

It doesnt seem right

but it works.


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INTAKE MANIFOLD

CONSTRUCTIONVariable induction

system


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EXHAUST MANIFOLD

CONSTRUCTIONSingle Exhaust

Dual Exhaust

Single w/crossoverHeaders

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