Crankshaft Main Bearing: Testing and Inspection
CLEARANCE1. To check main bearing-to-journal oil clearance, remove the main caps and bearing halves.
2. Clean each main journal and bearing half with a clean shop towel.
3. Place one strip of plastigage across each main journal.
NOTE: If the engine is still in the car when you bolt the main cap down to check the clearance, the weight of the crankshaft and drive plate will flatten the plastigage further than just the torque on the cap bolt and give you an incorrect reading. For an accurate reading, support the crank with a jack under the counterweights, and check only one bearing at a time.
4. Reinstall the bearings and caps, then torque the bolts.
NOTE: Do not rotate the crankshaft during inspection.
5. Remove the cap and bearings half, and measure the widest part of the plastigage.
Main Bearing-to-Journal Oil Clearance:
Standard (New): 0.020 - 0.044 mm (0.0008 - 0.0017 inch)
Service Limit: 0.050 mm (0.0020 inch)
6. If the plastigage measures too wide or too narrow, (remove the engine if it's still in the vehicle), remove the crankshaft, and remove the upper half of the bearing. Install a new, complete bearing with the same color code, and recheck the clearance.
7. If the plastigage shows the clearance is still incorrect, try the next larger or smaller bearing (the color listed above or below that one), and check again.
NOTE: If the proper clearance cannot be obtained by using the appropriate larger or smaller bearings, replace the crankshaft and start over.
SELECTION
CAUTION: If the codes are indecipherable because of an accumulation of dirt and dust, do not scrub them with a wire brush or scraper. Clean them only with solvent or detergent.
Crankshaft Bore Code Location
Letters or Bars have been stamped on the end of the block as a code for the size of each of the 4 main journal bores. Use them, and the numbers stamped on the crankshaft (codes for main journal size), to choose the correct bearings.