Connecting Rod Bearing Clearance

Engine connecting rod bearing clearances can be determined by use of Plastigage or equivalent. The following is the recommended procedure for the use of Plastigage:
1. Rotate the crankshaft until the connecting rod to be checked is at the bottom of its stroke.
2. Remove oil film from surface to be checked. Plastigage is soluble in oil.





3. Place a piece of Plastigage across the entire width of the bearing shell in the bearing cap approximately 6.35 mm (1/4 inch) off center and away from the oil hole. In addition, suspect areas can be checked by placing plastigage in the suspect area.
4. Before assembling the rod cap with Plastigage in place, the crankshaft must be rotated until the connecting being checked starts moving toward the top of the engine. Only then should the cap be assembled and torqued to specifications. Do not rotate the crankshaft while assembling the cap or the Plastigage may be smeared, giving inaccurate results.





5. Remove the bearing cap and compare the width of the flattened Plastigage with the scale provided on the package. Locate the band closest to the same width. This band indicates the amount of oil clearance. Differences in readings between the ends indicate the amount of taper present. Record all readings taken. Refer to Engine Specifications. Plastigage generally is accompanied by two scales. One scale is in inches, the other is a metric scale.

NOTE: Plastigage is available in a variety of clearance ranges. Use the most appropriate range for the specifications you are checking.