Micrometer Method For Main Bearings

MICROMETER METHOD





CAUTION: Do not shim, scrape, or file bearing inserts. Do not touch the bearing surface of the insert with bare fingers. Skin oil and acids will etch the bearing surface.

1. Measure the crankshaft main journal diameter with a micrometer in several places, approximately 90 degrees apart, and average the measurements.
2. Compute the taper and the out of round.
3. Install the crankshaft bearings into the crankshaft bearing cap and the engine block.

CAUTION: In order to prevent the possibility of cylinder block or crankshaft bearing cap damage, the crankshaft bearing caps are tapped into the cylinder block cavity using a brass, lead, or a leather mallet before the attaching bolts are installed. Do not use attaching bolts to pull the crankshaft bearing caps into the seats. Failure to observe this information may damage a cylinder block or a bearing cap.

4. Install the crankshaft bearing caps and the bolts. Ensure that the arrows on the crankshaft bearing caps are facing the front of the engine.

NOTE: Tighten inside bearing cap bolts first and outside bearing cap bolts last.

^ Tighten the bolts to 135 Nm (100 ft. lbs.).
5. Measure the bearing inside diameter (ID) using an inside micrometer.
6. Compare the crankshaft bearing clearance specifications.
7. If the bearing clearance is within specifications, the bearing is satisfactory. If the clearance is not within specifications, replace the bearing. Always replace both the upper and the lower bearings as a unit.
8. A standard or undersize bearing combination may result in the proper clearance. If the proper bearing clearance cannot be achieved using the standard or the undersize bearings, it will be necessary to replace or repair the crankshaft.