Crankshaft Measurement

Special Tools 

GE 7872  Magnetic Base Dial Indicator

For equivalent regional tools, refer to Special Tools

Fig 1: Crankshaft And Support
Courtesy of GENERAL MOTORS COMPANY
1. Using a suitable fixture, support the crankshaft.
Fig 2: Measuring Crankshaft Runout
Courtesy of GENERAL MOTORS COMPANY
2. Install the GE 7872  indicator.
3. Measure the crankshaft runout using the GE 7872  indicator. Refer to Engine Mechanical Specifications .
Fig 3: Crankshaft Thrust Wall Width And Surface
Courtesy of GENERAL MOTORS COMPANY
4. Measure the crankshaft thrust wall width (1) for wear using an inside micrometer. Refer to Engine Mechanical Specifications .
5. Measure the crankshaft thrust wall surface (2) for runout using the GE 7872  indicator. Refer to Engine Mechanical Specifications .
6. If the crankshaft journals are damaged or worn beyond specifications, the crankshaft may be ground 0.25 mm (0.010 in). There is only 1 size of oversized main bearings available for service.
Fig 4: Outside Micrometer To Inspect Crankshaft Main Journals
Courtesy of GENERAL MOTORS COMPANY
7. Inspect the crankshaft main journals for undersize, using an outside micrometer.
Fig 5: Inspecting Crankpins For Undersize
Courtesy of GENERAL MOTORS COMPANY
8. Inspect the crankpins for undersize using an outside micrometer.
9. Compare your measurements with those listed in the Engine Mechanical Specifications . If the crankpin journals are worn beyond the specifications, the crankshaft may be ground 0.25 mm (0.010 in). There is only 1 size of oversized connecting rod bearings available for service.
Fig 6: Measuring Main Bearing & Crankpin Journals For Out-Of-Round
Courtesy of GENERAL MOTORS COMPANY
10. Measure the main bearing and crankpin journals for out-of-round using the following procedure:
    1. Using an outside micrometer, measure the journal at the extreme front and rear locations on the journal. Call these points A and B.
    2. Measure the journal in 2 new locations exactly 90 degrees from the first points. Call these points C and D.
    3. Subtract A from C and B from D. The differences will indicate journal out-of-round.
    4. The out-of-round should not exceed 0.004 mm (0.00016 in) maximum.
    5. If the journals are worn beyond the specifications, the crankshaft may be ground 0.25 mm (0.010 in). There is only 1 size of oversized crankshaft and connecting rod bearings available for service.
11. Measure the main bearing and crankpin journals for taper using the following procedure:
    1. Using an outside micrometer, measure the journal at the extreme front (A) and rear (B) of the journal parallel to the crankshaft centerline.
    2. Subtract the smallest from the largest measurement. The result will be the journal taper.
    3. If the main bearing journal taper exceeds 0.004 mm (0.00016 in), replace the crankshaft.
    4. If the journals are worn beyond the specifications, the crankshaft may be ground 0.25 mm (0.010 in). There is only 1 size of oversized crankshaft and connecting rod bearings available for service.