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.

Fig 1: Locating Cylinder Block Main Bearing Bore Grade

Courtesy of CHRYSLER CORP.

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

Fig 2: Locating Crankshaft Main Journal Grade Marking

Courtesy of CHRYSLER CORP.

Service main bearings have a number from 1-5 marked in ink on the bearing surface. For verification, use chart for number to size identification.

Fig 3: Identifying Main Bearing Grade Marks

Courtesy of CHRYSLER CORP.

Fig 4: Selecting Main Bearing Grade

Courtesy of CHRYSLER CORP.

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.