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Chapter 11 Lower End Theory and Service Cylinder Block Disassembly • Position piston at BDC for removal • Remove connecting rod cap and cover rod bolts to prevent cylinder damage • Carefully push the piston and rod with wooden handle • Be sure connecting rod does not damage the cylinder wall Cylinder Block Disassembly (cont’d) • Remove the main bearing caps in the specified order • Some engines use a main bearing girdle or bedplate that houses the bearings • Carefully remove crank and store vertically • Remove the rear main oil seal and bearing inserts Cylinder Block Disassembly (cont’d) • Remove the block core plugs and oil plugs to ensure thorough cleaning Oil gallery plugs Block Reconditioning • Clean all threaded bores with a thread chaser • Bolt holes should be slightly chamfered • Aluminum blocks with damaged threads may require a threaded insert – called a Helicoil • Inspect the block for cracks and damage Installing Core Plugs • After cleaning, the block should have new core and oil plugs installed • Coat the plug or bore lightly with a nonhardening sealer Camshafts • Have a cam lobe for each exhaust and intake valve • Lobe height is proportional to valve lift • May drive distributor and/or oil pump • May be iron, steel, or hollow Lobe Terminology Timing Drive Mechanisms Camshaft Drives • Tensioners may be spring loaded and/or hydraulically operated • Maintains correct belt or chain tension • Have a drive side and a slack side • The tensioner is on the slack side Installation - Camshaft • Thoroughly coat with assembly lube • Lubricate the lifters • Carefully install cam to avoid bearing damage • Install the thrust plate and cam gear • Once installed, turn the cam by hand Balance Shafts • • • • Inspect each bearing and journal Check oil clearances with plastigage Apply a light coat of oil to the bearings Align the timing marks and set the shafts into position Typical balance shaft timing mark arrangement Types of Oil Pumps • Rotor-type oil pump • Gear-type oil pump Types of Oil Pumps (cont’d) • A pressure relief valve controls maximum pressure • Inspect relief valve, gears or rotor, pump housing, and gear to pump housing clearance • Ensure proper pickup screen placement • Use new gaskets and seals for pump and pickup ... Bearing Failure and Inspection Installing Main Bearings and Crankshaft • Plastigage is used to determine main and rod bearing clearances • Insert between the bearing and journal • Torque and then loosen... at BDC for removal • Remove connecting rod cap and cover rod bolts to prevent cylinder damage • Carefully push the piston and rod with wooden handle • Be sure connecting rod does not damage the... damage and cracks, or scuffing on sides of the piston • Use a piston ring expander to remove rings • Clean carbon from piston top and ring grooves • Measure ring side clearance – between the ring and