Crankshaft: Service and Repair

Fig. 23 Main Bearings:

Fig. 24 Main Bearings Cap Bolt Tightening Sequence:

1. Set main bearings in proper position on cylinder block, Fig. 23. If cylinder block, crankshaft or main bearing is reused, main bearing clearance must be measured. Upper bearings have oil groove.
2. If crankshaft, cylinder block and main bearing are replaced, thickness of main bearings must be selected as follows:
a. Grade No. of each cylinder block main journal is punched on respective cylinder block.
b. Grade No. of each crankshaft main journal is punched on respective crankshaft.
c. Select main bearing whose thickness grade is equal to sum of thickness grades of crankshaft journal and main journal.
3. Apply engine oil to main bearing surfaces on both sides of cylinder block and cap.
4. Install crankshaft and main bearing caps, torquing bolts to specifications in two or three stages in sequence, Fig. 24.
5. Ensure crankshaft turns smoothly by hand.
6. Measure crankshaft free endplay at No. 4 bearing. Clearance should be .0020-.0067 inch. If clearance exceeds .0118 inch, replace No. 4 main bearing.
7. Measure connecting rod side clearance. Clearance should be .0079-.0138 inch. If clearance exceeds .0157 inch, replace connecting rod and/or crankshaft.
8. Install pistons with connecting rods in proper cylinders, noting the following:
a. Ensure not to scratch cylinder wall with connecting rod.
b. Apply engine oil to cylinder wall, piston and bearing.
c. Arrange so that front mark on piston head faces toward front of engine.
d. Install connecting rod bearing caps and torque connecting rod nuts to 10-12 ft. lbs., then turn bolts 60-65° clockwise or if angle wrench is not available, tighten bolts to 28-33 ft. lbs.