Measuring Main Bearing Clearance - Gaging Plastic Method

WARNING: This page is about a different variant/trim than selected.

Fig 1: View Of Gaging Plastic Installed On Crankshaft Journal

Courtesy of GENERAL MOTORS CORP.

NOTE:

The crankshaft main bearings are a precision insert type. Main bearing caps are machined with the engine block for proper clearance and cannot be shimmed or filed for bearing fit. If the clearances are found to be excessive, new bearings and/or engine block and cap repair or replacement may be required.
Do not rotate the crankshaft while gaging plastic is between the crankshaft journal and the bearing surface.
The crankshaft bearing clearances are critical. Excessive bearing clearance may effect CKP sensor signals and may affect OBD II system operation.
Remove the bearing cap side bolts prior to cap removal.

Remove the bearing caps, bearing half, and bolts. Refer to Crankshaft and Bearing Removal .
Install gaging plastic onto the crankshaft journal. Install the gaging plastic the full width of the crankshaft bearing journal.
Install the bearing caps, bearing half, and bolts. Refer to Crankshaft and Bearing Installation .
Remove the bearing caps, bearing half, and bolts. Refer to Crankshaft and Bearing Removal .

Fig 2: Measuring Gaging Plastic

Courtesy of GENERAL MOTORS CORP.

Measure the gaging plastic at its widest area using the scale supplied with the plastic gaging kit.
- If the gaging plastic shows irregularity in the journal exceeding 0.025 mm (0.001 in), remove the crankshaft and measure the journal with a micrometer.
- If clearance cannot be brought to specifications, replace the crankshaft or engine block, as required. Refer to Engine Mechanical Specifications .