GM Full-Size Trucks 1970-1979 Repair Guide

Rocker Arms

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REMOVAL & INSTALLATION



Gasoline Engines

See Figures 1, 2, 3 and 4



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Fig. Fig. 1: Unfasten the retaining bolts ...



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Fig. Fig. 2: ... then remove the rocker arms



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Fig. Fig. 3: If necessary, remove the pushrods



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Fig. Fig. 4: Exploded view of rocker arm assembly

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the valve cover, as outlined earlier.
  4.  
  5. Unfasten the rocker arm flanged bolts, and remove the rocker pivots.
  6.  
  7. Remove the rocker arms.
  8.  

Remove each set of rocker arms (one set per cylinder) as a unit.

To install:
  1. Position a set of rocker arms (for one cylinder) in the proper location.
  2.  

Install the rocker arms for each cylinder only when the lifters are off the cam lobe and both valves are closed.

  1. Coat the replacement rocker arm and pivot with SAE 90 gear oil and install the pivots.
  2.  
  3. Install the flanged bolts and tighten alternately. Tighten the bolts to 25 ft. lbs. (34 Nm).
  4.  
  5. Install the valve cover, then connect the negative battery cable.
  6.  

Diesel Engines

When the diesel engine rocker arms are removed or loosened, the lifters must be bled down to prevent oil pressure buildup inside each lifter, which could cause it to raise up higher than normal and bring the valves within striking distance of the pistons.

  1. Remove the valve cover, as outlined earlier.
  2.  
  3. Remove the rocker arm pivot bolts, the bridged pivot and rocker arms.
  4.  
  5. Remove each rocker set as a unit.
  6.  

To install:
  1. Lubricate the pivot wear point and position each set of rocker arms in its proper location. Do not tighten the pivot bolts for fear of bending the valves when the engine is turned.
  2.  
  3. The lifters can be bled down for 6-cylinders at once with the crankshaft in either of the following two positions:
    1. For cylinders number 3, 5, 7, 2, 4 and 8, turn the crankshaft so the saw slot on the harmonic balancer is at 0 degrees on the timing indicator.
    2.  
    3. For cylinders 1, 3, 7, 2, 4 and 6, turn the crankshaft so the saw slot on the harmonic balancer is a 4 o'clock.
    4.  

  4.  
  5. Tighten the rocker arm pivot bolts VERY SLOWLY to 28 ft. lbs. (38 Nm). It will take 45 minutes to completely bleed down the lifters in this position. If additional lifters must be bled, rotate the engine to the other position, tighten the rocker arm pivot bolts, and again wait 45 minutes before rotating the crankshaft. Excess torque here can bend the pushrods, so be careful!
  6.  
  7. Assemble the remaining components in the reverse of disassemble. The rocker covers do not use gaskets, but are sealed with a bead of RTV (Room Temperature Vulcanizing) silicone sealer.
  8.  

 
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