Chevrolet Full-size Cars 1968-1978 Repair Guide

Valve Springs



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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.
  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.

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 15 lbs. is permissible on the spring covered in this guide.


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Fig. Fig. 4 With the valve spring out of the way, the valve stem seals may now be replaced

New valve seals must be installed when the valve train is put back together. Certain seals slip over the valve stem and guide boss, while others require that the boss be machined. In some applications Teflon guide seals are available. Check with a machinist and/or automotive parts store for a suggestion on the proper seals to use.

Remember that when installing valve seals, a small amount of oil is able to pass the seal to lubricate the valve guide; otherwise, excessive wear will result.

To install the valve and rocker assembly:

  1. Lubricate the valve stems with clean engine oil.
  3. Install the valves in the cylinder head, one at a time, as numbered.
  5. Lubricate and position the seals and valve springs, again a valve at a time.
  7. Install the spring retainers, and compress the springs.
  9. With the valve key groove exposed above the compressed valve spring, wipe some wheel bearing grease around the groove. This will retain the keys as you release the spring compressor.
  11. Using needlenosed pliers (or your fingers), place the keys in the key grooves. The grease should hold the keys in place. Slowly release the spring compressor; the valve cap or rotator will raise up as the compressor is released, retaining the key.
  13. Install the rocker assembly, and install the cylinder head(s).


In the event of cylinder head removal or any operation that requires disturbing or removing the rocker arms, the rocker arms must be adjusted. See the Valve Lash procedure earlier in this information.