Camshaft and Bearings Cleaning and Inspection: Notes

Special Tools

• J 7872:  Magnetic Base Dial Indicator Set
• J 8520:  Camshaft Lobe Lift Indicator

For equivalent regional tools, refer to Special Tools

Fig 1: View Of Camshaft Inspection Points
Courtesy of GENERAL MOTORS CORP.
1. Clean the components in solvent.
WARNING: Refer to Safety Glasses and Compressed Air Warning
2. Dry the components with compressed air.
3. Inspect the camshaft bearing journals (1) for scoring or excessive wear.
4. Inspect the camshaft valve lifter lobes (2) for scoring or excessive wear.
5. Inspect the camshaft position (CMP) actuator oil passages (3) for restrictions.
6. Inspect the threaded bolt hole (4) in the front of the camshaft for damaged threads or debris.
7. Inspect the camshaft sprocket pin (204) for damage.
8. Inspect the camshaft retainer plate for wear or a damaged sealing gasket.

   If the camshaft retainer plate sealing gasket is not cut or damaged, it may be used again.

Fig 2: Camshaft Bearings
Courtesy of GENERAL MOTORS CORP.
9. Inspect the camshaft bearings for the following:
   • Excessive wear, evidence of galling, pitting, scoring, or embedded debris. The appearance of the bearing material being different shades of gray are considered normal, and are not guideline for bearing replacement. Measure the bearing inside diameter (ID) as required for an over-sized condition. Refer to Engine Mechanical Specifications (RPO L20 VIN A)Engine Mechanical Specifications (RPO L96 VIN G)Engine Mechanical Specifications (RPO L9H)Engine Mechanical Specifications (RPO LC9 VIN 3)Engine Mechanical Specifications (RPO LMG VIN 0)Engine Mechanical Specifications (RPO LY6 VIN K) .
   • Proper fit in the engine block. Camshaft bearings have an interference fit to the engine block and should not be loose in the engine block bearing bores.
   • The oil lubrication feed hole in the bearing must be in alignment with the drilled out passage in the block.
   • The oil lubrication feed hole is not plugged by debris.
   • Bearings with excessive wear or scoring must be replaced.
   • Bearings with excessive wear, galling, pitting, scoring, or embedded debris must be replaced.
Fig 3: Measure Camshaft Journals With Micrometer
Courtesy of GENERAL MOTORS CORP.
10. Using a micrometer, measure the camshaft journals for wear and out-of-round. Refer to Engine Mechanical Specifications (RPO L20 VIN A) or Engine Mechanical Specifications (RPO L96 VIN G) or Engine Mechanical Specifications (RPO L9H) or Engine Mechanical Specifications (RPO LC9 VIN 3) or Engine Mechanical Specifications (RPO LMG VIN 0) or Engine Mechanical Specifications (RPO LY6 VIN K) .
    • If the camshaft bearing journals are out-of-round, replace the camshaft.
    • If the camshaft bearing journal diameter is not within specification, replace the camshaft.
Fig 4: Measuring Camshaft Lobes
Courtesy of GENERAL MOTORS CORP.
11. Using a micrometer, measure the camshaft lobes for wear. Refer to Engine Mechanical Specifications (RPO L20 VIN A) or Engine Mechanical Specifications (RPO L96 VIN G) or Engine Mechanical Specifications (RPO L9H) or Engine Mechanical Specifications (RPO LC9 VIN 3) or Engine Mechanical Specifications (RPO LMG VIN 0) or Engine Mechanical Specifications (RPO LY6 VIN K) .
Fig 5: Measuring Camshaft Runout
Courtesy of GENERAL MOTORS CORP.
12. Measure the camshaft runout.
    1. Mount the camshaft in wooden V-blocks or between centers on a fixture.
    2. Using the J 7872:  set , measure the runout of the intermediate camshaft bearing journals.
    3. If camshaft runout is not within specification, the camshaft is bent and should be replaced. Refer to Engine Mechanical Specifications (RPO L20 VIN A)Engine Mechanical Specifications (RPO L96 VIN G)Engine Mechanical Specifications (RPO L9H)Engine Mechanical Specifications (RPO LC9 VIN 3)Engine Mechanical Specifications (RPO LMG VIN 0)Engine Mechanical Specifications (RPO LY6 VIN K) .