Crankshaft Main Bearing: Description and Operation

DESCRIPTION





Bearing caps are not interchangeable and are marked to insure correct assembly (Fig. 65). Upper and lower bearing halves are NOT interchangeable.

CRANKSHAFT MAIN JOURNALS
The crankshaft journals should be checked for excessive wear, taper and scoring. Limits of taper or out-of-round on any crankshaft journals should be held to 0.015 mm (0.0006 inch). Journal grinding should not exceed 0.305 mm (0.012 inch) under the standard journal diameter. DO NOT grind thrust faces of Number 2 main bearing. DO NOT nick crank pin or bearing fillets. After grinding, remove rough edges from crankshaft oil holes and clean out all passages.

CAUTION: With a forged steel crankshaft it is important that the final paper or cloth polish after any journal regrind be in the same direction as normal rotation in the engine.





The crankshaft thrust is controlled with thrust washers located at the upper No. 2 main bearing bulk head (Fig. 66). All bearing cap bolts removed during service procedures are to be cleaned and oiled before installation. Bearing shells are available in standard and the following undersize: 0.025 mm (0.001 inch) and 0.254 mm (0.010 inch). Never install an undersize bearing that will reduce clearance below specifications.