Crankshaft Main Bearings

NOTE: Some production crankshafts are ground to .009" (.23 mm) undersize at the assembly plant. They are identified as follows: crankshaft counterweight of undersize journal, will be stamped on one side with the number "9", along with a large spot of Light Green paint. Main bearing cap will be painted Light Green on each side.

Measure main bearing clearances one at a time, while all other main caps are properly tightened. Mark or identify main bearing cap before removing. Support crankshaft weight, using a jack placed under counterweight next to the bearing being checked.
Start with rear main bearing (No. 5) and work forward. Also, remove drive belts from crankshaft pulley, prior to checking front (No. 1) bearing. Check main bearing clearance using Plastigage method. Install cap and tighten to specifications. Do not allow crankshaft to turn.
Remove cap and measure width of Plastigage with scale furnished. Undersize bearing halves may be used in combination to obtain correct clearance. Always replace both upper and lower bearing halves.
Upper main bearings are removed from cylinder block using Upper Main Bearing Remover/Installer (J-8080). Insert remover/installer in crankshaft oil hole and rotate crankshaft clockwise. If remover/installer is not available, a cotter pin may be bent, as necessary, to do the job.
Lubricate journal and bearings. Insert plain end of new bearing between crankshaft and notched side of block. Insert bearing remover/installer into crankshaft oil hole, and rotate bearing into place.
Install lower bearing half into cap. Install and tighten main bearing caps with arrows pointing toward front of engine. Check crankshaft end play after aligning thrust bearing. Check end play by prying crankshaft forward, and inserting feeler gauge between crankshaft counterweight and forward face of rear main bearing cap.