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Published byDewi Kusumo Modified over 5 years ago
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Modern Automotive Technology PowerPoint for by Russell Krick
Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois
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Chapter 14 Lesson 3 Engine Bottom End Construction
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Contents Crankshaft construction Engine bearing construction
Rear main bearing oil seal construction Select-fit parts Balancer shafts
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Crankshaft Construction
Engine crankshafts are usually made of cast iron or forged steel Forged steel crankshafts are needed for heavy-duty applications turbocharged or diesel engines
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Crankshaft Oil Passages
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Crankshaft Oil Flow Oil enters the crankshaft at the main bearings and passes through holes in the main bearing journals Oil then flows through passages in the crankshaft and out to the connecting rod bearings
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Engine Bearing Construction
There are three basic types of engine bearings: crankshaft main bearings connecting rod bearings camshaft bearings
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Engine Bearings
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Crankshaft Oil Passages
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Bearing Construction Steel is used for the body
Alloys are plated over the backing to form the bearing surface
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Bearing Crush Used to help prevent the bearing from spinning inside its bore The bearing is made slightly larger than the bearing bore When the rod or main cap is tightened, the bearing ends press against each other, locking the bearing in place
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Bearing Crush
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Bearing Spread Used on split-type engine bearings to hold the bearing in place during assembly The distance across the parting line of the bearing is wider than the bearing bore bearing spread causes the bearing insert to stick in its bore when pushed into place
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Standard Bearing Has the original dimensions specified for a new, unworn, or unmachined crankshaft May have the abbreviation “STD” stamped on its back
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Undersize Bearing Used on a crankshaft journal that has been machined to a smaller diameter Available in undersizes of 0.010", 0.020", 0.030" and sometimes 0.040" Undersize is normally stamped on the back of the bearing
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This bearing is for a journal that has been machined 0.010" undersize
Undersize Bearing This bearing is for a journal that has been machined 0.010" undersize
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Bearing Positioning A. Spread B. Lug C. Dowel
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Bearing Oil Holes and Grooves
Holes allow oil to flow through the block and into the clearance between the bearing and the journal Grooves provide a channel so oil can completely encircle the bearing before flowing over and out of it
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Bearing Oil Holes and Grooves
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Main Thrust Bearing and Washers
limits crankshaft end play thrust flanges are formed on the main bearing sides, almost touching the thrust surfaces machined on the crankshaft Thrust washers used instead of a thrust bearing to limit crank end play
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Main Thrust Bearing and Washers
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Washers slide into place between the crankshaft and block
Thrust Washers Washers slide into place between the crankshaft and block
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Rear Main Bearing Oil Seal Construction
The rear main bearing oil seal prevents oil leakage around the back of the crankshaft
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Rear Main Bearing Oil Seal
There are several different types of seals These types include: two-piece neoprene one-piece neoprene wick or rope seal
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Two-Piece Neoprene Seal
Has a lip to trap oil and another lip that keeps dust and dirt out of the engine
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Two-Piece Neoprene Seal
The seal fits into a groove cut into the block and rear main cap
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One-Piece Neoprene Seal
The seal fits around the rear flange on the crankshaft
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Wick Rear Oil Seal Woven rope filled with graphite
One piece of the rope seal fits into a groove in the block Another piece fits in a groove in the main cap Not as common on modern vehicles as one- and two-piece neoprene seals
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Select-Fit Parts Parts that are selected and installed in a certain position to improve the fit or clearance between parts pistons are commonly selected to fit precisely into their cylinders Because of select-fit parts, it is important that you reinstall parts in their original locations
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Balancer Shafts Used in some engines to cancel the vibrating forces produced by crankshaft, piston, and rod movement Usually found on 4- and 6-cylinder engines Usually, a chain is used to turn the shafts at twice crankshaft rpm
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Shafts are supported on bearings and lubricated by pressurized oil
Balancer Shafts Shafts are supported on bearings and lubricated by pressurized oil
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