Main Bearing Clearance Inspection: Notes

1. 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.
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.
3. Place one strip of plastigage across each main journal.
4. Reinstall the bearings and caps, then torque the bolt. See step  19 under CRANKSHAFT & PISTON. DO NOT rotate the crankshaft.
5. Remove the cap and bearing half, and measure the widest part of the plastigage. See Fig 1 and MAIN BEARING-TO-JOURNAL OIL CLEARANCE  table.
   MAIN BEARING-TO-JOURNAL OIL CLEARANCE
   
   

   Application	Specification - In. (mm)
   Standard (New)	.0008-.0017 (.020-.044)
   Service Limit	.0020 (.050)

6. If the plastigage measures too wide or too narrow, (remove the engine it it's still in the car), 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. Do not file, shim, or scrape the bearings or the caps to adjust 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. If the proper clearance cannot be obtained by using the appropriate larger or smaller bearings, replace the crankshaft and start over.

Fig 1: Removing Cap & Bearing Half

Courtesy of AMERICAN HONDA MOTOR CO., INC.