Chevrolet Blazer/Jimmy 1969-1982 Repair Guide

Valve Lash

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ADJUSTMENT



Gasoline Engines

All 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.

1969-71 MODELS

Normalize the engine temperature by running it for several minutes. Shut the engine off and remove the valve cover(s). After valve cover removal, tighten the cylinder heads to specification. The use of oil stopper clips, readily available on the market is recommended to prevent oil splatter when adjusting valve lash. Restart the engine. Valve lash is set with the engine warm and idling.

Turn the rocker arm nut counterclockwise until the rocker arm begins to clatter. Reverse the direction and turn the rocker arm down slowly until the clatter just stops. This is the zero lash position. Turn the nut down an additional 1 / 4 turn and wait ten seconds until the engine runs smoothly. Continue with additional 1 / 4 turns, waiting ten seconds each time, until the nut has been turned down one full turn from the zero lash position. This one turn, pre-load adjustment must be performed to allow the lifter to adjust itself and prevents possible interference between the valves and pistons. Noisy lifters should be cleaned or replaced.

1972-82 MODELS


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Fig. Fig. 1 When adjusting the valves, check for lash at the pushrod



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Fig. Fig. 2 Valve arrangement-6 cylinder engines



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Fig. Fig. 3 Valve arrangement-V8 engines

  1. Remove the rocker covers and gaskets.
  2.  
  3. Adjust the valves on six cylinder engines as follows:
  4.  
    1. Mark the distributor housing with a piece of chalk at 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 No. 1 cylinder and the points are open. 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 No. 6 cylinder and the points are open. The following valves can be adjusted:

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

    8.  
    9. Adjust the valves on V8 engines as follows:
    10.  
      1. Crank the engine until the mark on the damper aligns with the TDC or 0° mark on the timing tab and the engine is in 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 No. 1 firing position. If the valves move, it is in No. 6 firing position and the crankshaft should be rotated one more revolution to the No. 1 firing position.
      2.  
      3. The adjustment is made in the same manner as 6 cylinder engines.
      4.  
      5. With the engine in No. 1 firing position, the following valves can be adjusted:

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

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

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

      8.  
      9. Reinstall the rocker arm covers using new gaskets.
      10.  
      11. Install the distributor cap and wire assembly.
      12.  



 
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