For 1990-2009 cars

### Connecting Rod Bearings

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

Notice: Do not scrape, shim, or file bearing inserts. If the bearing surface of the insert is touched with bare fingers, the skin oil and acids will etch the bearing surface.

1. 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.

2. 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 tangs and wear grooves)

3. 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 Bearing Removal and to Crankshaft and Bearing Installation .

Important: Carefully investigate bearing failure, other than normal wear.

4. Inspect the connecting rods or main bearing bores. Complete the following steps:

4.1. | Torque the bearing cap to specifications.

4.2. | Measure the bore for taper and out of round.

4.3. | Ensure that taper or out of round does not exist.

5. Inspect the bearing cap bolts. Replace the bolts, if the bolts are stretched.
6. 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.

1. Method A -- yields measurements from which the bearing clearance can be computed.
2. 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° 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.

Notice: 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 use this process may damage a cylinder block or a bearing cap.

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

#### Tools Required

J 36660-A Torque Angle Meter

Notice: Do not scrape, shim, or file bearing inserts. If the bearing surface of the insert is touched with bare fingers, the skin oil and acids will etch the bearing surface.

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: Upper and lower inserts may be different. Do not obstruct any oil passages.

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.
4. Make sure the insert tangs are engaged.
5. 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.

Notice: 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 use this process may damage a cylinder block or a bearing cap.

8. Install the bearing cap. Tap the cap gently into place with a suitable tool.
9. Install the bearing cap bolts.

Tighten
Tighten the bolts to 35 N·m (26 lb ft). Use the J 36660-A in order to tighten the bolts an additional 50°.

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.