Camshaft Gear/Sprocket: Service and Repair

To check for worn camshaft lobes without disassembling the engine, refer to "Measuring Camshaft Lobe Lift."


Remove or Disconnect
1. Front end sheet metal as required, depending on body builder design.
^ Drain the cooling system.
2. Radiator, fan shroud, fan, and pulley.
3. Air cleaner.
4. Fuel pump.
5. Rocker arm cover, as outlined previously.
6. Distributor.
7. Pushrod covers, as outlined previously.
8. Hydraulic lifters, as outlined previously.
9. Torsional damper, as outlined previously.
10. Timing gear cover, as outlined previously.





^ Align the timing marks.






11. Thrust plate bolts (39).
12. Camshaft. Support the camshaft carefully to avoid damage to the camshaft bearings. On some vehicles, it may be necessary to disconnect the front engine mounting and raise the engine to provide clearance.

Inspect
- Camshaft lobes and journals for scratches, pitting, and wear.
- Timing gear for damaged teeth.

Measure






^ Thrust plate to camshaft clearance. Use a feeler gage. The proper clearance is 0.003-0.008-inch. If the clearance is excessive, replace the thrust plate. If the clearance is insufficient, replace the spacer ring. Refer to the proper unit repair manual.

Camshaft Gear And Thrust Plate Replacement
^ Refer to the proper unit repair manual.

Camshaft Bearing Replacement
^ Refer to the proper repair manual.


Install or Connect

^ Coat the camshaft lobes and journals with a high quality engine oil supplement (GM Engine Oil Supplement or equivalent).

1. Camshaft (90) to the engine. Handle the camshaft carefully to prevent damage to the camshaft bearings.

Important





^ Line up the timing marks on the crankshaft gear and camshaft gear.

2. Thrust plate bolts (94).

Tighten
^ Thrust plate bolts to 9.0 N.m (80 in. lbs.).

Measure
- Camshaft and crankshaft gear run-out. Use ai dial indicator. Camshaft gear run-out should not exceed 0.10 mm (0.004-inch), crankshaft gear run-out should not exceed 0.08 mm (0.003-inch). If gear run out is excessive, the gear will have to be removed and any burrs cleaned from the shaft or the gear will have to be replaced.
- Timing gear backlash. Use a dial indicator. The correct backlash is 0.10-0.15 mm (0.004-0.006-inch) with new parts, 0.20 mm (0.008-inch) maximum with used parts.

4. Timing gear cover, as outlined previously.
5. Torsional damper, as outlined previously.
6. Hydraulic lifters, as outlined previously.

Important
^ Replace all hydraulic lifters, change the crankcase oil and filter, and add GM Engine Oil Supplement (or equivalent) to the engine oil if a new camshaft was installed.

7. Pushrod covers, as outlined previously.
8. Distributor.
9. Rocker arm cover, as outlined previously.
10. Fuel pump.
11. Air cleaner.
12. Radiator, fan, pulley, and shroud.
^ Fill the cooling system with the proper quantity and grade of coolant.
13. Front end sheet metal, as required.