Tools Required

J 8087  Cylinder Bore Gage. See Special Tools and Equipment .

Fig 1: View Of Crankshaft & Bearings
Courtesy of GENERAL MOTORS CORP.
1. Clean the crankshaft of the following elements:
   • Oil
   • Sludge
   • Carbon
2. Inspect the crankshaft oil passages for obstructions.
3. Inspect the crankshaft keyway for nicks or wear.
4. Inspect the crankshaft threads.
IMPORTANT: If cracks, severe gouges or burned spots are found, the crankshaft must be replaced. Slight roughness may be removed with a fine polishing cloth soaked in clean engine oil. Burrs may be removed with a fine oil stone.
5. Inspect the crankshaft bearing journals and the crankshaft thrust surfaces for the following conditions:
   • Cracks
   • Chips
   • Gouges
   • Roughness
   • Grooves
   • Overheating, discoloration
6. Inspect the corresponding crankshaft bearings for embedded foreign material and determine the source.
IMPORTANT: Note the location of the crankshaft main bearing high spots. If they are not in line, the crankshaft is bent and must be replaced.
7. Inspect the crankshaft bearings for uneven side-to-side wear. This may indicate a bent crankshaft or a tapered bearing journal.
Fig 2: View Of Crankshaft Bearings
Courtesy of GENERAL MOTORS CORP.
IMPORTANT: The crankshaft bearings are the precision insert type. The crankshaft bearings are available in standard and various undersizes.
8. Inspect the outer surfaces of the crankshaft bearings for the following conditions:
   • Wear - surface wear indicates either movement of the insert or high spots in the surrounding material, spot wear.
   • Overheating or discoloration
   • Looseness or rotation indicated by flattened tangs and wear grooves
9. Inspect the thrust surfaces of the main thrust bearing for the following conditions:
   • Wear
   • Grooving, grooves are caused by irregularities of the crankshaft thrust surface.
Fig 3: Inspecting Crankshaft Main Bearing Bores
Courtesy of GENERAL MOTORS CORP.
IMPORTANT: If crankshaft bearing failure is due to other than normal wear, investigate the cause. Inspect the crankshaft or connecting rod bearing bores.
10. Using the J 8087  inspect the connecting rod bearing bores or crankshaft main bearing bores using the following procedure:
    1. Tighten the bearing cap to specification.
    2. Measure the bearing bore using J 8087  for taper and out-of-round. See Special Tools and Equipment .
    3. No taper or out-of-round should exist.