Isuzu Cars and Trucks 1981-1991

Rocker Arms/Shafts

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REMOVAL AND INSTALLATION
4-Cylinder Gasoline Engines, Except DOHC
  1. Disconnect the negative battery cable. Remove the rocker cover.
  2.  
  3. Loosen the rocker arm shaft bracket nuts a little at a time, in sequence, starting with the outer nuts.
  4.  
  5. Remove the nuts from the rocker arm shaft brackets. Remove shaft assembly.
  6.  
  7. To disassemble the rockers and shafts; remove the spring from the rocker arm shaft, the rocker brackets and arms. Keep parts in order for reassembly.
  8.  



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Fig. Rocker arm and shaft assembly gasoline 4-cyl. engine, except DOHC



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Fig. Rocker arm assembly gasoline 4-cyl. engine, except DOHC



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Fig. Rocker arm shaft installation gasoline 4-cylinder engine, except DOHC



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Fig. Rocker arm bolt torque sequence gasoline 4-cyl. engine, except DOHC

  1. Before installing apply a generous amount of clean engine oil to the rocker arm shaft, rocker arms and valve stems.
  2.  

To install:

  1. Install the longer shaft on the exhaust valve side and the shorter shaft on the intake side so the aligning marks on the shafts are turned on the front side of the engine.
  2.  
  3. Assemble the rocker arm shaft brackets and rocker arms to the shafts so the cylinder number, on the upper face of the brackets, points toward the front of the engine.
  4.  
  5. Align the mark on the No. 1 rocker arm shaft bracket with the mark on the intake and exhaust valve side rocker arm shaft.
  6.  
  7. Make certain the amount of projection of the rocker arm shaft beyond the face of the No. 1 rocker arm shaft bracket, is longer on the exhaust side shaft than on the intake shaft when the rocker arm shaft stud holes are aligned with the rocker arm shaft bracket stud holes.
  8.  
  9. Place the rocker arm shaft springs in position between the shaft bracket and rocker arm.
  10.  
  11. Check that the punch mark on the rocker arm shaft is facing upward, then, install the rocker arm shaft bracket assembly onto the cylinder head studs. Align the mark on the camshaft with the mark on the No. 1 rocker arm shaft bracket.
  12.  
  13. Torque the rocker arm shaft brackets-to-cylinder head nuts to 16 ft. lbs. (21 Nm) and bolts to 72 inch lbs. (8 Nm).
  14.  


NOTE
Hold the rocker arm springs while torquing the nuts to prevent damage to the spring. Start with the center nut and work outward.

  1. Adjust the valves as outlined in . Install the rocker arm cover, with a new gasket and sealer. Check the ignition timing.
  2.  

Diesel Engine
  1. Disconnect the negative battery cable. Remove the cam cover.
  2.  
  3. Loosen the rocker arm shaft bracket nuts a little at a time, in sequence, commencing with the outer brackets.
  4.  
  5. Remove the nuts from the rocker arm shaft brackets.
  6.  
  7. Disassemble the rocker arm shaft assembly by removing the spring from the rocker arm shaft and then removing the rocker arm brackets and arms.
  8.  
  9. Inspect the rocker arm shaft for runout. Support the shaft on V-blocks at each end and check runout by slowly turning it with the probe of a dial indicator. Replace the shaft with a new one if the runout exceeds 0.4mm (0.0156 in.). Runout should not exceed 0.2mm (0.0079 in.).
  10.  
  11. Inspect the rocker arm shaft for wear, replace the shaft if obvious signs of wear are encountered.
  12.  



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Fig. Bolt loosening sequence for removing rocker arm assembly diesel engine

To install:

  1. Use a liberal amount of clean engine oil to coat the shaft, rocker arms and valve stems. Install the longer shaft on the exhaust valve side, shorter shaft on the intake side, so that the aligning marks on the shafts are turned to the front of the engine.
  2.  
  3. Torque the rocker arm shaft bracket and stud nuts to 15 and 1922 ft. lbs. (20 and 1927 Nm). Hold the rocker arm springs with an adjustable wrench while torquing the nuts to prevent damage to the springs. Torque the nuts a little at a time in sequence, beginning with the center bracket and working outward.
  4.  
  5. Adjust valve clearances, reinstall the cam cover and check for leaks.
  6.  

V6 Engine
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the rocker arm covers.
  4.  
  5. Remove the rocker arm nut, the pivot balls, the rocker arm and the pushrods. Keep all components separated so they may be reinstalled in the same location.
  6.  


NOTE
The intake and exhaust pushrods are of different lengths.

To install:

  1. Install the pushrods in their original location; be sure the lower ends are seated in the lifter.
  2.  
  3. Coat the bearing surfaces of the rocker arms and pivot balls with Molykote or equivalent.
  4.  
  5. Install the rocker arm nuts and torque them to 14 and 1920 ft. lbs. (20 and 1927 Nm).
  6.  
  7. Adjust the valve lash as outlined in .
  8.  



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Fig. Exploded view of the cylinder head/rocker arm assembly V6 engine

 
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