GM Full-Size Trucks 1980-1987 Repair Guide

Rocker Arms

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REMOVAL & INSTALLATION



Gasoline Engines

See Figures 1, 2 and 3

  1. Remove the valve cover.
  2.  
  3. Remove the rocker arm nuts, then remove the rocker pivots.
  4.  



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Fig. Fig. 1: Remove the rocker arm nut and pivot



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Fig. Fig. 2: With the nut and pivot out of the way, the rocker arm may be removed

  1. Remove the rocker arms.
  2.  

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

To install:
  1. To install, 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. Loosely install the rocker arm nuts, then properly adjust the valve lash. Please refer to the procedure later in this section.
  4.  



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Fig. Fig. 3: Six-cylinder rocker arm components-all gasoline V8's similar

8-350 Diesel

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. Disconnect the negative battery cable.
  2.  
  3. Remove the valve cover.
  4.  
  5. Remove the rocker arm pivot bolts, the bridged pivot and rocker arms.
  6.  
  7. Remove each rocker set as a unit.
  8.  
  9. To install, 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.
  10.  
  11. 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.  

  12.  
  13. Tighten the rocker arm pivot bolts VERY SLOWLY to 28 ft. lbs. 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!
  14.  
  15. 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.
  16.  

8-379 (6.2L) Diesel

See Figure 4

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Fig. Fig. 4: 6.2L diesel rocker shaft assemblies

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the valve cover as previously explained.
  4.  
  5. The rocker assemblies on the 379 differ completely from those on the 350 diesel. The 379 arms are mounted on two short rocker shafts per cylinder head, with each shaft operating four rockers. Remove the two bolts which secure each rocker shaft assembly, and remove the shaft.
  6.  
  7. The rocker arms can be removed from the shaft by removing the cotter pin on the end of each shaft. The rocker arms and springs slide off.
  8.  
  9. To install, make sure first that the rocker arms and springs go back on the shafts in the exact order in which they were removed.
  10.  

Always install new cotter pins on the rocker shaft ends.

  1. Install the rocker shaft assemblies, tightening the bolts to 41 ft. lbs.
  2.  

 
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