39. Camshaft and Bearings Cleaning and Inspection
Camshaft and Bearings Cleaning and Inspection
Special Tools
* J 7872 - Magnetic Base Dial Indicator Set
* J 8520 - Camshaft Lobe Lift Indicator
For equivalent regional tools, refer to Special Tools (Special Tools).
1. Clean the components in solvent.
Warning: Refer to Safety Glasses Warning (Safety Glasses Warning).
2. Dry the components with compressed air.
3. Inspect the camshaft bearing journals (3) for scoring or excessive wear.
4. Inspect the camshaft valve lifter lobes (2) for scoring or excessive wear.
5. On camshaft with single-bolt cam sprocket, inspect the threaded bolt hole (5) in the front of the camshaft for damaged threads or debris.
6. On camshaft with 3-bolt cam sprocket, inspect the threaded bolt holes (4) in the front of the camshaft for damaged threads or debris.
7. Inspect the camshaft sprocket pin (1) 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.
Note:
* On LS3 and LS9 engines the camshaft bearings are lead-free, the lining is composed of a aluminum-tin material. The appearance of the bearing material being different shades of gray are considered normal, and are not a guideline for bearing replacement.
* On LS7 engine, the camshaft bearings are composed of a lining material that uses a lead babbitt with copper matrix backing. The presence of the copper color bearing material should be considered normal, and not a guideline for bearing replacement. Measure the bearing inside diameter (ID) as required for an over-sized condition. Refer to Engine Mechanical Specifications (6.2L LS3) (Service Limits & General Specifications)Engine Mechanical Specifications (6.2L LS9) (Service Limits & General Specifications)Engine Mechanical Specifications (7.0L) (Service Limits & General Specifications).
9. Inspect the camshaft bearings for the following conditions:
* 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 a guideline for bearing replacement. Measure the bearing inside diameter (ID) as required for an over-sized condition. Refer to Engine Mechanical Specifications (6.2L LS3) (Service Limits & General Specifications)Engine Mechanical Specifications (6.2L LS9) (Service Limits & General Specifications)Engine Mechanical Specifications (7.0L) (Service Limits & General Specifications).
* 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 oil passage in the block.
* The oil lubrication feed hole is not plugged by debris.
* Bearings with excessive wear, galling, pitting, scoring, or embedded debris must be replaced.
10. Using a micrometer, measure the camshaft journals for wear and out-of-round. Refer to Engine Mechanical Specifications (6.2L LS3) (Service Limits & General Specifications)Engine Mechanical Specifications (6.2L LS9) (Service Limits & General Specifications)Engine Mechanical Specifications (7.0L) (Service Limits & General Specifications).
* 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.
11. Using a micrometer, measure the camshaft lobes for wear. Refer to Engine Mechanical Specifications (6.2L LS3) (Service Limits & General Specifications)Engine Mechanical Specifications (6.2L LS9) (Service Limits & General Specifications)Engine Mechanical Specifications (7.0L) (Service Limits & General Specifications).
12. Measure the camshaft runout.
1. Mount the camshaft in wooden V-blocks or between centers on a fixture.
2. Using the J 7872 - indicator , 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 (6.2L LS3) (Service Limits & General Specifications)Engine Mechanical Specifications (6.2L LS9) (Service Limits & General Specifications)Engine Mechanical Specifications (7.0L) (Service Limits & General Specifications).
Measuring Camshaft Lobe Lift
Note: Measuring camshaft lobe lift is a procedure used to determine if the camshaft lobes have worn. This test is to be performed prior to engine disassembly and with the camshaft and valve train components installed in the engine.
1. Using the J 8520 , measure camshaft lobe lift.
2. Remove the valve rocker arms and bolts.
3. Install the dial indicator mounting stud into the valve rocker arm bolt hole.
4. Assemble the components of the J 8520 - indicator and position onto the stud.
5. Position the shaft of the dial indicator onto the end of the pushrod.
6. Rotate the face of the dial indicator to zero.
7. Slowly rotate the crankshaft clockwise, until the dial indicator obtains its highest and lowest readings.
8. Compare the total to specifications. Refer to Engine Mechanical Specifications (6.2L LS3) (Service Limits & General Specifications)Engine Mechanical Specifications (6.2L LS9) (Service Limits & General Specifications)Engine Mechanical Specifications (7.0L) (Service Limits & General Specifications). The total lobe lift is the difference between the highest and lowest reading.