GM Full-Size Trucks 1988-1998 Repair Information

Valve Lash

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All engines described here 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 rocker arms will have to be adjusted.

ADJUSTMENT



4.8L Engines
  1. Remove the rocker arm cover.
  2.  
  3. Mark the distributor housing at the No. 1 and No. 6 wire positions and remove the cap.
  4.  
  5. Turn the crankshaft until the rotor points to the No. 1 position. The following valves can be adjusted:

    No. 1 exhaust and intake
     
    No. 2 intake
     
    No. 3 exhaust
     
    No. 4 intake
     
    No. 5 exhaust
     

  6.  

To adjust a valve, back off the adjusting nut until lash (play) is felt at the pushrod. Tighten the nut just until all lash is removed. This can be determined by rotating the pushrod with your fingers. When all lash is removed, the pushrod will stop rotating. When all play is removed, tighten the nut 1 full turn (360°).

  1. Rotate the crankshaft until the rotor points to the No. 6 position. The following valves can be adjusted:

    No. 2 exhaust
     
    No. 3 intake
     
    No. 4 exhaust
     
    No. 5 intake
     
    No. 6 intake and exhaust
     

  2.  

  1. Install the distributor cap.
  2.  
  3. Install the rocker cover.
  4.  

V6 and V8 Engines

See Figure 1

  1. Remove the rocker covers and gaskets.