Chevrolet Full-size Cars 1968-1978 Repair Guide

Rocker Arms

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REMOVAL & INSTALLATION





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Fig. Fig. 1 Exploded view of the various rocker arm components-representative of all engines



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Fig. Fig. 2 After removing the valve cover, loosen the rocker arm adjusting nut and ...



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Fig. Fig. 3 ... pull the rocker arm off the stud-inspect the stud for damage, and replace it if necessary



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Fig. Fig. 4 Also inspect the pushrod for any signs of wear or damage before reinstalling the components

All Engines

Rocker arms are removed by removing the adjusting nut. Be sure to adjust the valve lash after replacing the rocker arms. Coat the replacement rocker arm and ball with SAE 90 gear oil before installation. Make sure the valves are closed on the cylinder you are working on before installation.

When replacing an exhaust rocker, move an old intake rocker to the exhaust rocker arm stud and install the new rocker arm on the intake stud. This will prevent burning of the new rocker arm on the exhaust position.

Rocker arms studs that have damaged threads or are loose in the cylinder heads may be replaced by reaming the bore and installing oversize studs. Oversizes available are 0.003 in. and 0.013 in. The bore may also be tapped and screw-in studs installed. Several aftermarket companies produce complete rocker arm stud kits with installation tools. Mark IV use screw-in studs and pushrod guide plates.

ADJUSTMENT



Most engines described in this guide use hydraulic lifters, which require no periodic adjustment. In the event of cylinder head removal or any operation that requires disturbing the rocker arms, the valves will have to be adjusted, except on the 307 Oldsmobile produced engine.

Solid Lifters (1968-71 Engines)

These are initial adjustments usually required after assembling an engine or doing a valve job. They should be followed up by an adjustment with the engine running as described above. If the camshaft was replaced with an aftermarket high performance one, the adjustment procedure is the same except you will need the camshaft manufacturer's clearance specifications.

  1. Set the engine to the No. 1 firing position.
  2.  
  3. Adjust the clearance between the valve stems and the rocker arms with a feeler gauge. Check the Chart for the proper clearance. Adjust the following valves in the No. 1 firing position: Intake No. 2, 7, Exhaust No. 4, 8.
  4.  
  5. Turn the crankshaft 1 / 2 revolution clockwise. Adjust the following valves: Intake No. 1, 8, Exhaust No. 3, 6.
  6.  
  7. Turn the crankshaft 1 / 2 revolution clockwise to No. 6 firing position. Adjust the following valves in the NO. 6 firing position: Intake No. 3, 4, Exhaust No. 5, 7.
  8.  
  9. Turn the crankshaft 1 / 2 revolution clockwise, Adjust the following valves: Intake No. 5, 6, Exhaust No. 1, 2.
  10.  
  11. Run the engine until the normal operating temperature is reached. Reset all clearances, using the procedure listed above under Engine Running.
  12.  

Hydraulic Lifters (1968-78 Engines)


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Fig. Fig. 5 Inline six-cylinder engine valve adjustment



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Fig. Fig. 6 V8 engine valve adjustment-small block shown, big block similar

  1. Remove the rocker covers and gaskets.
  2.  
  3. Adjust the valves on inline 6-cylinder engines as follows:
  4.  
    1. Mark the distributor housing with a piece of chalk at the No. 1 and 6 plug wire positions. Remove the distributor cap with the plug wires attached.
    2.  
    3. Crank the engine until the distributor rotor points to the NO. 1 cylinder and the No. 1 piston is at TDC (both No. 1 cylinder valves closed). At this point, adjust the following valves:
    4.  




No. 1-Exhaust and Intake
 
No. 2-Intake
 
No. 3-Exhaust
 
No. 4-Intake
 
No. 5-Exhaust
 

  1. c. Back out the adjusting nut until lash is felt at the pushrod, then turn the adjusting nut in until all lash is removed. This can be determined by checking pushrod end-play while turning the adjusting nut. When all play has been removed, turn the adjusting nut in 1 full turn.
  2.  
  3. Crank the engine until the distributor rotor points to the no. 6 cylinder and the no. 6 piston is at TDC (both No. 6 cylinder valves closed). The following valves can be adjusted:
  4.  



No. 2-Exhaust
 
No. 3-Intake
 
No. 4-Exhaust
 
No. 5-Intake
 
No. 6-Intake and Exhaust
 

  1. Adjust the valves on V8 engines as follows:
  2.  
    1. Crank the engine until the mark on the damper aligns with the TDC or 0 degree mark on the timing tab and the engine is in the No. 1 firing position. This can be determined by placing the fingers on the No. 1 cylinder valves as the marks align. If the valves do not move, it is in the No. 1 firing position. If the valves move, it is in the No. 6 firing position and the crankshaft should be rotated one more revolution to the No. 1 firing position.
    2.  
    3. With the engine in the No. 1 firing position, the following valves can be adjusted:
    4.  




V8-Exhaust: 1, 3, 4, 8
 
V8-Intake: 1, 2, 5, 7
 

    1. c. Back out the adjusting nut until lash is felt at the pushrod, then turn the adjusting nut in until all lash is removed. This can be determined by checking pushrod end-play while turning the adjusting nut. When all play has been removed, turn the adjusting nut in:
    2.  




1 / 2 -1 1 / 4 additional turn (flat lifter)
 

    1. d. Crank the engine 1 full revolution until the marks are again in alignment. This is the No. 6 firing position. The following valves can now be adjusted:
    2.  




V8-Exhaust: 2, 5, 6, 7
 
V8-Intake: 3, 4, 6, 8
 

  1. Reinstall the rocker arm covers using new gaskets or sealer.
  2.  
  3. Install the distributor cap and wire assembly.
  4.  
  5. Adjust the carburetor idle speed.
  6.  

 
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