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Bumping clearance

Bumping clearance= clearance volume. If more- volumetric efficiency drops, if less- piston hits the head.  Cause of change in bumping clearance during service- 1, wear in crank pin bearing( symptoms slow decrease in oil pressure and knocking sounds in later stages). 2, change in size of head gaskets. 3. wear in main bearing. effects of large clearances-FAD decreases, air outlet temperature increases. checking bumping clearances- using a lead wire pressed between head and piston inserted through the valve opening and connecting rod jacked up using a crowbar correcting clearances: cylinder head gaskets to be changed size, inserting shims between big end of con-rod
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