Tools Required

J 7872  Magnetic Base Dial Indicator Set

1. With the camshaft in a suitable fixture, measure the camshaft for wear.
   Fig 1: Identifying Camshaft In Suitable Fixture

   Courtesy of GENERAL MOTORS CORP.
2. Measure the camshaft journals for diameter and out-of-round using an outside micrometer.
   • If the diameter is smaller than 26.948 mm (1.061 in), replace the camshaft.
   • If the out-of-round exceeds 0.022 mm (0.0009 in), replace the camshaft.
   Fig 2: Measuring Camshaft Journals

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3. Measure the camshaft runout using J 7872.  Refer to Engine Mechanical Specifications  .
   Fig 3: Measuring Camshaft Runout

   Courtesy of GENERAL MOTORS CORP.
4. Measure the camshaft thrust wall width (1) for wear using an inside micrometer. Refer to Engine Mechanical Specifications  .
5. Measure the camshaft thrust wall surface (2) for runout using J 7872.  Refer to Engine Mechanical Specifications  .
6. If the camshaft is damaged or worn beyond specifications, replace the camshaft. No machining of the camshaft is allowed.
   Fig 4: Measuring Camshaft Thrust Wall Width & Surface

   Courtesy of GENERAL MOTORS CORP.
7. Measure the camshaft lobes for wear using the J 7872. 
   Fig 5: Identifying J 7872

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8. Place the J 7872  with the indicator tip on the base circle (2) of the camshaft lobe.
   1. 8.1. Place the J 7872  dial at zero.
   2. 8.2. Rotate the camshaft until the indicator tip is at the highest point on the lobe. This reading is the lift (1) of the camshaft lobe.
   3. 8.3. The specifications for lift are as follows:
      • Intake camshaft: 6.154 mm (0.2423 in).
      • Exhaust camshaft: 5.944 mm (0.2336 in).
9. If the indicated measurement is significantly lower than these specifications, replace the camshaft or engine performance will be reduced.
   Fig 6: Measuring Camshaft Lobe

   Courtesy of GENERAL MOTORS CORP.