15 Engine Front End Construction Chapter

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Objectives After studying this chapter, you will be able to: Explain the function and construction of a vibration damper. Compare the three types of camshaft drives. Explain the construction of a timing gear, timing chain, and timing belt assembly.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Objectives Summarize the construction of engine front covers, oil slingers, and other related components. Describe safety practices related to working on engine front end components. Correctly answer ASE certification test questions on engine front end construction.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Engine Front End Assembly Camshaft drive mechanism Front cover-mounted oil pump Water pump Auxiliary shafts Supercharger

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Vibration Damper Construction Harmonic vibration –High-frequency movement resulting from twisting and untwisting of crankshaft Vibration not controlled, crankshaft could vibrate like musician’s tuning fork

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Vibration Damper Construction (Cont.) Vibration damper or harmonic balancer –Heavy wheel mounted on rubber ring –Controls harmonic vibration Dual-mass harmonic balancer –One weight mounted on outside of crankshaft pulley and another on inside

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Vibration Damper Construction (Cont.) Balancer keys into crankshaft snout Rubber ring –Separates outer inertia ring and inner sleeve Crankshaft pulley –Operates belts for alternator, water pump, air conditioning compressor, and other units (Chrysler)

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Camshaft Drives Transfers rotational motion from crankshaft to camshaft(s) –Camshaft drive must rotate camshaft(s) at one-half of engine speed

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Timing gears Gears drive engine camshaft –Timing marks show technician how to install gears properly Crankshaft gear –Keyed to crankshaft snout Camshaft gear –Cam gear twice the size of crank gear Results in desired 2:1 reduction

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Timing Chain and Sprockets Crankshaft sprocket keys to crankshaft snout Larger camshaft sprocket, with either metal or plastic teeth, bolts to camshaft Timing chain transfers power from crankshaft sprocket to camshaft sprocket

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Timing Chain and Sprockets (Cont.) Most common type of camshaft drive arrangement on cam-in block engines May also be used in OHC engines (Chrysler)

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Timing Chain and Sprockets (Cont.) Chain guide –May be needed to prevent chain slap Chain slap –Occurs when chain flaps back and forth due to excessive slack Chain tensioner –Takes up slack in chain as it and sprockets wear Spring-loaded plastic or fiber block

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

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Engine Front Cover Construction Also called timing cover –Encloses timing chain or gear mechanism –Prevents oil leakage from front of engine Front oil seal –Prevents oil leakage between crankshaft and front cover

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Oil Slinger Washer-shaped part that fits in front of crankshaft sprocket –Oil squirts out of front main bearing and strikes spinning slinger –Centrifugal force throws oil outward onto timing chain or gears

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Timing Belt and Sprockets Timing belt drive mechanism –Drives camshaft on OHC engines Timing belt sprockets –Usually made of cast iron or aluminum –Crank sprocket Keyed to crankshaft snout –Camshaft sprocket Bolts to front of camshaft

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Timing Belt and Sprockets (Cont.) Timing belt –Smooth and accurate method of turning camshaft Belt tensioner –Spring loaded Keeps belt firmly seated Timing belt cover –Protects belt and technician (Honda)