Connecting Rod Bearing: Service and Repair

STANDARD PROCEDURE - CONNECTING RODS AND BEARINGS

CONNECTING ROD BEARINGS





The bearing caps are not interchangeable and should be marked at removal to insure correct assembly.

The bearing shells must be installed with the tangs inserted into the machined grooves in the rods and caps. Install cap with the tangs on the same side as the rod.

Fit all rods on one bank until complete.

Limits of taper or out-of-round on any crankshaft journals should be held to specification limits. Bearings are available in 0.007 mm oversize (0.0003 in oversize), standard, 0.007 mm (0.0003 in) undersize 0.025 mm (0.001 in) undersize, and 0.254mm (0.010 in undersize. Install the bearings in pairs. Do not use a new bearing half with an old bearing half. Do not file the rods or bearing caps.

1. For measuring main bearing clearance and connecting rod bearing clearance use plastigage. For more information on using plastigage Measuring Bearing Clearance Using Plastigage. Refer to Engine Specifications for bearing clearance specifications Engine Specifications.

SELECT FIT ROD BEARINGS





1. Connecting rod bearings use select fit to achieve improved clearance control. On a new engine, the crankshaft journal is gaged to use a specific bearing size. The grade is indicated on the #9 counterweight (2) of the crankshaft and listed from left to right with the recommended size.




How to Determine Rod Bearing Class





This example shows how to determine the bearing class needed for each rod bearing, assuming that a new crankshaft is being installed in a new or existing engine block. If the code 'B' 'A' 'B' 'B' 'B' 'C' is stamped on the #9 counterweight of the crankshaft (3), then rod #1 would require Class 2 bearings, rod #2 would require Class 1 bearings, rod #3 would require Class 2 bearings, rod #4 would require Class 2 bearings, rod #5 would require Class 2 bearings, and rod #6 would require Class 3 bearings.





CONNECTING ROD BOLTS

NOTE: The rod bearing bolts should be examined before reuse. If the threads are necked down the bolts must be replaced.





1. Examine connecting rod bolts for stretching. Stretching can be checked by holding a scale or straight edge against the threads. If all the threads do not contact the scale the bolt must be replaced.
2. Before installing the bolts the threads should be cleaned and inspected.
3. Install clean bolts finger tight. Then alternately torque each bolt to assemble the cap properly.
4. Tighten the connecting rod cap bolts to specification. Engine Specifications

CONNECTING ROD SIDE CLEARANCE





1. Mount a dial indicator to a stationary point on engine. Locate probe perpendicular to and resting against the connecting rod cap being checked. Move connecting rod all the way to rear of its travel (toward flywheel end of crank). Zero the dial indicator. Move connecting rod forward of to limit of travel (toward pulley end of crank) and read the dial indicator. Compare measurement to specification listed in engine specifications Engine Specifications. Repeat procedure for each connecting rod. Turn crankshaft for connecting rod accessibility.