Crankshaft Main Bearing: Service and Repair

CRANKSHAFT MAIN BEARING FITTING





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

The grade marks for the cylinder block main bearing bore grade is located on the pan rail just below the left side engine mount bracket. These marks 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 are read left to right, corresponding with journal number 1, 2, 3, 4.

MAIN BEARING SELECTION CHART - 2.7L






Refer to the MAIN BEARING SELECTION CHART - 2.7L to properly select the main bearings. For an example, if the main bore grade is 3 and the journal grade is 2, the proper select fit bearing would be (2) +0.003 mm (+0.0002 in.). Each bearing grade increment of 0.003 mm is for wall thickness so diametrical clearances are adjusted 0.006 m per select fit class.





NOTE: Service main bearings have a number from 1-5 marked in ink on the bearing surface. For verification, use the MAIN BEARING SELECTION CHART - 2.7L for number to size identification.

The upper main bearing (2) has a oil feed hole and a center groove (3) to allow lubrication of the main journal and must be properly positioned in the block.

NOTE: Although cylinder bores are graded for size, there is only one piston size.