Nissan Z - ZX 1970-1988 Repair Guide

Valves

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REMOVAL & INSTALLATION



Except VG Engines

See Figure 1

  1. Refer to the Cylinder Head removal and installation procedures in this section, then remove the cylinder head and place it on a workbench.
  2.  
  3. Using a medium size prybar (as a lever) and the camshaft (as the pivot point), compress the valve springs and remove the rocker arms.
  4.  



Click image to see an enlarged view

Fig. Fig. 1: Compress the valve spring-1970-83 models

If the rocker arms are difficult to remove, it may be necessary to loosen the rocker arm pivot lock nut and screw the pivot down to make clearance. After removing the rocker arms, be careful not to loose the valve rocker guide.

  1. Remove the camshaft sprocket and the camshaft thrust plate, then remove the camshaft by pulling it through the rear of the cylinder head.
  2.  


WARNING
When removing the camshaft, be careful not to damage the camshaft lobes.

  1. Using Valve Spring Compressor tool No. ST12070000 or equivalent, compress the valve springs and remove the valve collets.
  2.  
  3. Carefully release the spring pressure, then remove the valves retainers, the springs, the valve and etc.
  4.  

Be sure to keep the parts in order for installation purposes. Install new valve oil seals.

  1. To install, use new gaskets and reverse the removal procedures.
  2.  

If the rocker arm pivot lock nut was loosened, the valve clearance must be adjusted.

VG Engine

See Figure 2

  1. Refer to the Cylinder Head removal and installation procedures in this section, then remove the cylinder head and place it on a workbench.
  2.  
  3. Remove the rocker arm assemblies with the valve lifter guide and valve lifter.
  4.  

When removing the rocker arm assemblies and the valve lifter guide, be sure to keep the parts in order, for they are not interchangeable.

  1. Using Valve Spring Compressor tool No. KV10110600 or equivalent, mount it on the cylinder head and compress the valve springs, then remove the valve collets.
  2.  
  3. Carefully release the spring pressure, then remove the valves retainers, the springs, the valve and etc.
  4.  



Click image to see an enlarged view

Fig. Fig. 2: Compressing the valve spring-1984-88 models

Be sure to keep the parts in order for installation purposes. Install new valve oil seals.

  1. To install, use new gaskets and reverse the removal procedures.
  2.  

INSPECTION



See Figures 3 and 4

  1. Check the valves for worn, damaged or deformed valve head or stem.
  2.  



Click image to see an enlarged view

Fig. Fig. 3: Valve stems may be rolled on a flat surface to check for bends



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Fig. Fig. 4: Use a micrometer to check the valve stem diameter

If the valve head is worn down to a marginal thickness of 0.02 in. (0.5mm), replace the valve. The grinding allowance for the valve stem is 0.02 in. (0.5mm) (all engines-except VG engines) or 0.008 in. (0.2mm) (for VG engines), otherwise replace the valve.

  1. Reface or replace the valve if the damage is excessive.
  2.  

RESURFACING



See Figures 5 and 6

  1. Using a wire power brush, clean all of the dirt and carbon deposits from the valve.
  2.  
  3. Using a valve grinding machine, grind a new mating face on the valve head; the marginal thickness of the head cannot be less than 0.5mm.
  4.  



Click image to see an enlarged view

Fig. Fig. 5: Resurface the valve using a valve grinding machine



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Fig. Fig. 6: Profile view of a valve

  1. Using a valve grinding machine, grind the stem end of the valve; the stem end cannot be ground more than 0.5mm (all engines-except VG) or 0.2mm (VG).
  2.  

 
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