GM Chevy Mid-Size Cars 1964-1988 Repair Guide

Valve Lash Adjustment

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See Figures 1, 2 and 3

Although some of the earlier vehicles covered by this guide are equipped with solid lifters that are adjusted as a part of routine engine tune-ups, most engines described in this guide use hydraulic lifters, which require no periodic adjustment. However, on all vehicles, in the event of cylinder head removal or any operation requiring the rocker arms to be disturbed, adjustment of the arms will be necessary to assure proper valve operation.



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Fig. Fig. 1: Valve arrangement of the Chevrolet-built V6 engines (E-Exhaust, I-Intake)



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Fig. Fig. 2: Valve arrangement-263 V6 diesel engine



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Fig. Fig. 3: Valve arrangement-V8 diesel engine

SOLID LIFTERS (1964-71)



For vehicle's equipped with solid lifters, refer to the valve lash adjustment procedures in Engine Electrical of this guide.

HYDRAULIC LIFTERS (1972 AND LATER)



See Figure 4

The valve lash adjustment procedure is for hydraulic lifters which are filled with oil either from previous use (old lifters on which the oil has not drained) or from priming before installation (new lifters or old lifters on which oil had drained while removed from the engine).

  1. Remove the rocker covers and gaskets.
  2.  
  3. Adjust the valves on inline 6-cylinder engines as follows:
  4.  



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Fig. Fig. 4: Adjust the valve lash on hydraulic lifter engines by tightening the rocker arm nut while turning the pushrod by hand to determine lash

  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:

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

  4.  
  5. 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.
  6.  
  7. 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:

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

  8.  

  1. Adjust the valves on V6 and V8 engines as follows:
    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 (No. 4 on V6) and the crankcase 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:

      V8 - Exhaust: 1, 3, 4, 8
       
      V8 - Intake: 1, 2, 5, 7
       
      V6 - Exhaust: 1, 5, 6
       
      V6 - Intake: 1, 2, 3
       
      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 / 2 -1 1 / 4 additional turn (flat lifter)
       
      3 / 4 -1 1 / 4 additional turn (roller lifter V8)
       
      3 / 4 additional turn (roller lifter V6)
       
      Crank the engine 1 full revolution until the marks are again in alignment. This is the No. 6 firing position (No. 4 on V6). The following valves can now be adjusted:
       
      V8 - Exhaust: 2, 5, 6, 7
       
      V8 - Intake: 3, 4, 6, 8
       
      V6 - Exhaust: 2, 3, 4
       
      V6 - Intake: 4, 5, 6
       

    4.  

  2.  
  3. Reinstall the rocker arm covers using new gaskets or sealer.
  4.  
  5. Install the distributor cap and wire assembly.
  6.  
  7. Adjust the carburetor idle speed.
  8.  

 
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