Procedures

STANDARD PROCEDURE - CRANKSHAFT MAIN BEARING FITTING





The main bearings are a "select fit" to achieve proper oil clearances. For main bearing selection, the block and crankshaft have grade identification marks.


The marks for the cylinder block main bore grade are located on the left side pan rail. These grade marks (1, 2, or 3) are read left to right, corresponding to main bore 1, 2, 3, 4.


The grade marks for the crankshaft are located on the rearmost crankshaft counter weight as shown in. The crankshaft journal grade marks (A, B, or C) are read left to right, corresponding with journal number 1, 2, 3, 4.


Refer to the MAIN BEARING SELECTION CHART to properly select the main bearings. For an example, if the main bore grade is 3 and the journal grade is B, the proper select fit bearing would be a (2) +0.003 mm (+0.0002 in.).


NOTE: Service main bearings have a number from (1-5) marked in ink on the bearing surface. For verification, refer to the MAIN BEARING SELECTION CHART for number to size identification.





The upper main bearing has a oil feed hole and a center groove to allow lubrication of the main journal and must be properly positioned in the block.