Main & Connecting Rod Bearings

Thoroughly clean crankshaft and blow out oil passages with compressed air. Check crankshaft for runout with a dial indicator on second or third main bearing journal. If runout exceeds 0.004" (0.10 mm), straighten or replace crankshaft.
Check main and connecting rod bearing journals for taper or out-of-round. If taper or out-of-round exceeds 0.0004" (0.01 mm), crankshaft must be ground to next undersize.
Main and connecting rod bearing clearance is checked by the Plastigage method. If clearance exceeds specifications, replace bearings. If crankshaft wear is excessive and clearance cannot be brought to specifications by use of new standard size bearings, crankshaft must be reground to next undersize. Bearings are available in 0.002", 0.010" and 0.020" (0.05, 0.25 and 0.50 mm) undersize.
NOTE: All main bearings are different. No. 1 (Front) and No. 4 (Rear) have oil holes and must be installed toward block. Arrow on connecting rod cap must face front.