GM Full-Size Trucks 1970-1979 Repair Guide

Valve Springs

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REMOVAL & INSTALLATION



Valve spring removal and installation is part of the valve removal and installation procedure. Please refer to the appropriate procedure in this section.

TESTING



See Figures 1, 2 and 3



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Fig. Fig. 1: Use a caliper gauge to check the valve spring free-length



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Fig. Fig. 2: Check the valve spring for squareness on a flat service; a carpenter's square can be used



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Fig. Fig. 3: The valve spring should be straight up and down when placed like this

  1. Place the valve spring on a flat, clean surface next to a square.
  2.  
  3. Measure the height of the spring, and rotate it against the edge of the square to measure distortion (out-of-roundness). If spring height varies between springs by more than 1 / 16 in. or if the distortion exceeds 1 / 16 in., replace the spring.
  4.  

A valve spring tester is needed to test spring test pressure, so the valve springs must usually be taken to a professional machine shop for this test. Spring pressure at the installed and compressed heights is checked, and a tolerance of plus or minus 5 lbs. (22 N) is permissible on the springs covered in this guide.

 
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