Connecting Rod Bearing Replacement

Engine bearings are the precision insert type. The bearings are available for service use in standard and 0.001 inch undersize.





1. Remove the oil pan. Refer to Oil Pan Replacement.
2. Remove connecting rod caps. Rotate the crank to gain access to caps as necessary.
3. Inspect the connecting rods or main bearing bores. Complete the following steps:
4. Inspect bearing surfaces for the following conditions:
- Wear
- Gouges
- Embedded foreign material - If foreign material is found, determine its nature and source. Inspect the oil pan sludge and residue.
- Uneven side to side wear - If uneven wear is found, check for a bent crankshaft or tapered bearing journals.
5. Inspect the outer surfaces for the following conditions:
- Wear - Surface wear indicates either movement of the insert or high spots in the surrounding material (spot wear).
- Overheating (discoloration)
- Looseness or rotation (flattened tags and wear grooves)
6. Inspect the thrust surfaces (main thrust bearing) for the following conditions:
- Wear
- Grooving - Grooves are caused by irregularities of the crankshaft thrust surface. Refer to Crankshaft and Bearings Clean and Inspect.
6.1. Torque the bearing cap to specifications.
6.2. Measure the bore for taper and out of round.
6.3. Ensure that taper or out of round does not exist.





7. Inspect the bearing cap bolts (1 and 2). Replace the bolts, if the bolts are stretched.
8. In order to determine if a bolt is stretched, compare it to a new bolt.

Bearing Clearance
In order to determine the correct replacement insert size, measure the bearing clearance accurately. Either of the following two methods may be used: however, method A gives more reliable results and is preferred.
- Method A-yields measurements from which the bearing clearance can be computed.
- Method B-yields the bearing clearance directly. Method B does not give any indication of bearing or journal runout.

Method A
1. Measure the crankshaft journal diameter with a micrometer in several places.
2. Ensure the measurements are approximately 90 degrees apart.
3. Average the measurements.
4. Measure taper and runout
5. Ensure that the bearing inserts are installed in the correct bore, and torqued to specification.
6. Measure the bearing insert ID with an inside micrometer.
7. Measure using new inserts, if the inserts are being replaced.
8. If the readings are within limits. select a suitable set of inserts.
9. Bearing sets are available in standard and undersize in order to keep clearances within limits.
10. If clearances cannot be brought into specifications with selectively fitting bearings, replace the crankshaft.

Method B
1. Install all the bearing inserts and the crankshaft into the block.
2. Place a piece of gaging plastic across the entire bearing width.
3. Seat the bearing cap carefully. Tap the bearing cap lightly with a suitable tool.

Important: Do not rotate the crankshaft.

4. Tighten the bearing cap bolts to specification.
5. Remove the bearing cap.
6. Leave the gaging plastic in place. It does not matter whether the gaging plastic adheres to the journal or to the bearing cap.
7. Measure the flattened gaging plastic at its widest point with the scale printed on the gaging plastic package.
8. Remove all traces of the gaging plastic after measuring.

Bearing Installation Procedure

- Tools Required
- J 36660-A Torque Angle Meter

Important: Ensure that the bearing cap bolt holes and the cap mating surfaces are clean and dry.

1. Dip the bearing cap bolts in clean engine oil.

Notice: Refer to Upper/Lower Insert Notice in Service Precautions.

2. Place inserts into the bearing cap and into the engine block or connecting rod.
3. The inserts will project slightly when put into place. Ensure that the inserts project an equal distance on both sides. Make sure the insert tags are engaged.
4. In the case of a main bearing insert of the thrust bearing type, coat the thrust surface with GM approved lubricant or equivalent.
6. Lubricate the bearing surface with clean engine oil.
7. Install the crankshaft or connecting rod.
8. Install the bearing cap. Tap the cap gently into place with a suitable tool.

Notice: Refer to Fastener Notice in Service Precautions.

9. Install the bearing cap bolts.
- Tighten the bearing cap bolts to 27 Nm (20 ft. lbs.). Use the J 36660-A in order to tighten the bearing cap bolts an additional 50 degrees.
10. Seat the crankshaft thrust bearing by tapping the crankshaft in both directions with a wooden mallet.
11. Pry the connecting rod back and forth and check for binding. If necessary, loosen and retighten the bearing cap.
12. Measure the crankshaft end play.





13. Measure the connecting rod side clearance.
14. Install the oil pan. Refer to Oil Pan Replacement.