Bearing Selection

WARNING: This page is about a different car, the 2003 Pontiac Sunfire and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

Measure the bearing clearance to determine the correct replacement bearing insert size. There are two methods to measure bearing clearance. Method A gives more reliable results and is preferred.
- Method A yields measurement from which the bearing clearance can be computed.
- Method B yields the bearing clearance directly. Method B does not give any indication of bearing run-out.
Important: Do not mix inserts of different nominal size in the same bearing bore.
To measure bearing clearance using Method A, use the following procedure:
1. 2.1. Measure the crankshaft bearing journal diameter with a micrometer in several places, 90 degrees apart. Average the measurements.
  
  Fig 1: Measuring Crankshaft Bearing Journal Diameter
  Courtesy of GENERAL MOTORS CORP.
2. 2.2. Measure the crankshaft bearing journal taper and runout.
3. 2.3. Install the lower crankcase and tighten the bearing cap bolts to specification.
4. 2.4. Measure bearing I.D. in several places 90 degrees apart, average measurements.
5. 2.5. Subtract journal measurement from bearing I.D. measurement to determine clearance.
6. 2.6. Determine whether clearance is within specification.
7. 2.7. If out of spec choose different inserts.
8. 2.8. Measure the connecting rod inside diameter in the same direction as the length of the rod with an inside micrometer.
9. 2.9. Measure the crankshaft main bearing inside diameter with an inside micrometer.
To measure bearing clearance using Method B, use the following procedure:
1. 3.1. Clean the used bearing inserts.
2. 3.2. Install the used bearing inserts.
3. 3.3. Place a piece of gaging plastic across the entire bearing width.
4. 3.4. Install the bearing caps.
  
  Fig 2: Measuring Gaging Plastic
  Courtesy of GENERAL MOTORS CORP.
  
  NOTE: 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.
5. 3.5. Install the bearing cap bolts to specification.
  Important: Do not rotate the crankshaft.
6. 3.6. Remove the bearing cap, leaving the gaging plastic in place. It does not matter whether the gaging plastic adheres to the journal or to the bearing cap.
7. 3.7. Measure the gaging plastic at its widest point with the scale printed on the gaging plastic package.
8. 3.8. Remove the gaging plastic.