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Chapter 15:Engine Front End Construction

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Anastasia Hawkins

on 15 October 2013

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Transcript of Chapter 15:Engine Front End Construction

Chapter 15:Engine Front End Construction
be able to explain the functions and construction of the vibration damper
Compare the three types of the camshaft drives
Explain the construction of a timing gear, timing belt, and timing chain assembly
Summarize the construction of engine front covers, oil slingers, and other related components
Describe safety practices related to working on engine front end construction
Correctly answer ASC certification questions
What does it consist of??
The parts that attach to the front end of the engine (i.e. camshaft drive mechanism, front cover mounted oil pumps, water pumps, auxiliary shaft, ect.
Vibration damper Construction
Harmonic vibration, a high frequency movement resulting from twisting and untwisting of a crankshaft
Vibration Damper and Harmonic Balancer
Used to control harmonic vibrations
Cuts bad variation on the engine timing belt
Chain or gears a heavy wheel mounted on a rubber ring and is key to the crankshaft shout and this makes the damper spin with the crankshaft
Dual Mass Harmonic Balancer
Has one weight mounted on the outside of the crankshaft pulley and another in the inside
Shelby Brown,Anastasia Hawkins, Colt Hon, Cole Crosswait
Crankshaft pulley
Operates belt for the alternator, water pump, and other units
Often part of the harmonic balancer, may be bolted to the front of the balancer
the pulley either has a V or ribbed grooves for the belts
Camshaft Drive Construction
Must turn the camshaft at least one half of the crankshafts speed, must do this smoothly and independently
Consists of timing gears, timing chain and sprokets, timing belt and sprockets
Timing gears
Used to drive engine's camshaft
Common in heavy duty applications such as taxi cabs and trucks
keep to crankshaft snout
On the end of the camshaft and is twice the size of the crank gear
Timing Marks
Marks maybe circles, indentions, or lines on the gears
MUST be TOGETHER for timing
Timing Chain and Sprockets
Can also be used to turn the camshaft
Most common type of camshaft drive arrangement on the cam in the block engines
May also be used in OHC engines
Keyed to the crankshaft snout
Larger camsprockets with either heavy metal or plastic teeth bolts to camshaft
have timing marks
must line up properly to time correctly
Chain Guide and Chain Slap
A chain guide is needed to prevent chain slaps
chain slap occurs when the chain flaps back and forth because of excessive slack in the chain
chain guides allow the chain to slide on the guide with minimum friction and wear
Chain Tensioner
can be used to take up chain slack and sprockets wear
usually a spring loaded plastic or fiber block
Auxiliary Chain
may be used to drive the engine oil pump, balancer shaft, and other units on the engine
Driven by an extra sprocket usually placed in front of the crankshaft timing chain sprocket
DO NOT confuse with a timing CHAIN
Engine Front Cover Pt. 1
Encloses timing chain or gear mechanism and prevents oil leakage from the front of the engine
it bolts to the front of the engine block
it holds the front oil seal, probe holder, timing pointer, and other parts
Engine front cover or timing cover Pt2
A front oil seal prevents oil leakage between the chrankshaft and front cover
it is a press fin in the cover
the engine front cover is commonly made with thin stamped seal or cast aluminum

oil slinger
A washer shaped part that fits in front of the crankshaft sprocket.
When engine is running oil squirts out of the front main bearing and strikes the spinning slinger
Oil Slinger Cont.
Centrifugal force then throws the oil outward and onto the timing chain or gears
Timing Belt
Provide a very smooth and accurate method of turning the camshaft.
Have ragged or square teeth that prevent belt slippage
Timing belt Continued
Made of fiber glass-rain-forced, natural rubber, increased strength and durability
Some designed for a service life of over 100,000 miles if not damaged by raod debris or oil
Timing Belt Sprocket Pt.1
Usually made of cast iron or aluminum
Is keyed to the crank shaft snout, normally bolts to the front of the camshaft
Timing Belt Sprockets Pt.2
A dapin may be used to position camsprocket correctly
Belt sprocket and timing marks just like timing gears and chain and chain sprockets
Marks must be aligned specific points in the engine, this will properly time the opening of the engine valves
Belt Tensioner Part 1
A spring loaded wheel that keeps timing belt firmly seated on it's sprocket
Tensioner pushes inward on the back of the belt
Prevents from slipping on the sprocket teeth
Belt tensioner part 2
A tentioner's wheel is mounted on anti friction bearing
The bearing is filled with grease which is permanently sealed at the factory
Some use both spring tensioner and hydrolic pressure to maintain tightness on sprockets
Belt Tensioner part 3
Spring tension keeps belts tight when engine is shut off
Adjust belt tension with engine speed
At higher RPM, tension is increased to keep belt from flying off
The timing belt may be used to drive the oil pump, Diesel injection pump, or ignition distributor
Timing Belt Cover Part 1
Simply protects the belt from damage and the technician from injury
It is made of sheet metal and plastic
A gasket may seal the mating surfaces between the timing belt cover and the block
Timing Belt cover part 2
Timing belt covers are tightly sealed at the bottom to keep road debris and water off the belt
If ice forms on the belt sprockets it can cause the belt to jump off it's sprockets upsetting the valve timing which can lead to severe engine damage
Timing Marks
Marks may be circles, inendtions, or lines on the gears
Must line up together for timing
Thank you
Now please flip to te back of chapter ten and answer the ASC certification questions
Full transcript