by Russell Krick Publisher The GoodheartWillcox Co Inc

by Russell Krick Publisher The Goodheart-Willcox Co. , Inc. Tinley Park, Illinois © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

© Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

q Engine front end q Vibration damper construction q Camshaft drive construction © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

q Consists of the parts that attach to the front of the engine q These parts include: m camshaft drive mechanism m front cover-mounted oil pump m water pump m auxiliary shaft © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

q Harmonic vibration is a high-frequency movement resulting from twisting and untwisting of the crankshaft q If harmonic vibration is not controlled, the crankshaft could vibrate m vibration can result in serious damage, such as a broken crankshaft © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Vibration Damper q Also called a harmonic balancer q Keyed to the crankshaft snout q Controls harmonic vibration q Cuts load variation on the engine timing belt, chain, or gears, so these parts last longer © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Vibration Damper Constructed of a heavy wheel mounted on a rubber ring © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Vibration Damper © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Damper Operation q A rubber ring separates the outer inertia ring and the inner sleeve q The inertia ring and the rubber ring set up a damping action on the crankshaft as it tries to twist and untwist m damping action deadens vibrating © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Dual-Mass Balancer q Has one weight mounted on the outside of the crankshaft pulley and one weight on the inside q An extra rubber-mounted weight helps reduce vibration at high engine speeds © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Crankshaft Pulley q Operates belts for the alternator, water pump, and other units q May be part of the harmonic balancer, or bolted to the front of the balancer q Provides either V or ribbed grooves for the belts © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

q The camshaft drive must turn the camshaft at one-half of the crankshaft speed q There are three types of camshaft drives: m timing gears m timing chain and sprockets m timing belt and sprockets © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Timing Gears q Commonly used for heavy-duty applications m trucks, taxicabs, and diesel engines q Very dependable and long-lasting design q Noisier than a chain or belt drive © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Timing Gears q Two timing gears are used to drive the camshaft m one on the crankshaft and one on the camshaft q The cam gear is twice the size of the crank gear m provides a 2: 1 reduction © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Timing Gears Timing marks show the technician how to install the gears properly © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Timing Chain and Sprockets q Used to turn the camshaft q The crank sprocket is keyed to the crankshaft snout q The cam sprocket, with either metal or plastic teeth, bolts to the camshaft q The timing chain transfers power from the crank sprocket to the cam sprocket © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Timing Chain and Sprockets Timing marks must line up to time the camshaft with the crankshaft © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Timing Chain and Sprockets q Chain guide m may be needed to prevent chain slap q Chain tensioner m may be used to take up the slack in the chain as it and the sprockets wear m spring tension is used to push a plastic or fiber block outward, keeping a constant tension on the chain © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

OHC Timing Chain © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

DOHC Timing Chain © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Auxiliary Chain q May be used to drive the engine oil pump, balancer shafts, and other units on the engine q Driven by an extra sprocket, usually placed in front of the crankshaft timing chain sprocket © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Auxiliary Chain © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Engine Front Cover q Also called a timing cover q Bolts to the front of the engine q Encloses the timing chain or gear mechanism q Prevents oil leakage from the front of the engine q Made of thin, stamped steel or cast aluminum © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Engine Front Cover Holds the front oil seal, timing pointer, probe holder, and other parts © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Engine Front Cover This front cover houses the oil pump and water pump © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Timing Belt and Sprockets Used to drive the camshaft on OHC engines © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Timing Belt q Provides a very smooth and accurate method of turning the camshaft q Some belts are made of fiberglassreinforced nitrile rubber m some have a service life of 100, 000 miles (160, 000 km) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Timing Belt Sprockets q Usually made of cast iron or aluminum q The crank sprocket is keyed to the crankshaft snout q The cam sprocket bolts to the camshaft m a dowel pin may be used to position the sprocket correctly q Timing marks must be aligned with specific points on the engine to properly time the opening of the valves © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Belt Tensioner q The tensioner is a spring-loaded wheel that keeps the timing belt firmly seated on its sprockets m pushes inward on the back of the belt m prevents the belt teeth from slipping on the sprocket teeth m mounted on a sealed antifriction bearing © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Belt Tensioner q Some tensioners use both spring tension and hydraulic pressure q Hydraulic pressure adjusts the belt tension with engine speed q At higher rpms, belt tension is increased to keep the belt from slipping or flying off © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

OHC Engine This engine uses a belt-drive for the camshaft and the auxiliary shaft © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only

Timing Belt Cover q Protects the belt from damage q Protects the technician from injury q Made from sheet metal or plastic q Tightly sealed at the bottom to keep road debris and water off the rubber belt © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only