How to Replace Rod Bearings

by William Zane

Connecting rod bearings are extremely important components of any engine, whether it's a Toyota or a Ferrari engine. Rod bearings ensure that the rods operate smoothly around the crankshaft on one end, and the piston wrist pins on the other end. Replacing the bearings on a motor is standard procedure for any engine rebuild.

Remove the connecting rods from the pistons and crankshaft, if they are not already out. The rod's "big ends" (the larger end) are bolted to the crank with two bolts that hold the end cap on. The "small end" is held onto the wrist pin. The wrist pin is held onto the piston with two circlips. Remove these clips and slide the wrist pin out of the piston and the end of the rod. This should free the rod.

Remove the old bearings. You can use a screwdriver and a hammer to GENTLY tap out the old bearings. Tap on the edge of the bearing where it meets the end cap and vice-versa. Do not tap the bearing out from the side.

Clean the bearing surface of the rods on either end with a lint free rag. Carefully examine the bearing surfaces to make sure that there is absolutely no dirt or debris, as this can potentially cause bearing failure and shorten the life of the motor. Clean the bearings before installation, as well.

Slide one bearing into the end of the rod's big end and one bearing into the end cap. The end cap and the rod end form the circle that goes around the crankshaft when everything is bolted together. The bearings have a small notch on either end. These notches should be opposite of each other when the rod and end cap are put together, NOT on the same side. This is important for proper oil pressure. Repeat this process for all of the rods. Make sure the bearings fit snugly within the connecting rod and do not have any loose play.

The bearing on the small end of the rod should be pressed out with a press. If you do not have access to a press, you may be able to press the bearing out with a socket that just barely fits over the bearing, but is large enough to fit through the end of the rod. Carefully tap the bearing out and then tap in a new one. Be very careful not to damage the bearing.

Install the rods on the crank with Plastigage (See Resources) between the crank and the rod. Tighten the rod bolts to the manufacturer's specifications. Remove the rod and check the Plastigage to make sure that the tolerances are correct.

Reinstall the rods to the crankshaft and the pistons and writs pins, using engine assembly lube. Tighten the rod bolts according to the manufacturer's specifications.

About the Author

William Zane has been a freelance writer and photographer for over six years and specializes primarily in automotive-related subject matter among many other topics. He has attended the Academy of Art College in San Francisco, where he studied automotive design, and the University of New Mexico, where he studied journalism.