GM Chevy Mid-Size Cars 1964-1988 Repair Guide

Valves

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REMOVAL & INSTALLATION



See Figures 1, 2, 3, 4, 5 and 6

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.

  1. Remove the head(s), and place on a clean surface.
  2.  
  3. Using a suitable spring compressor (either a leverage or jawed type that is designed for pushrod overhead valve engines), compress the valve spring and remove the valve spring cap key. Carefully release the spring compressor and remove the valve spring and cap (and valve rotator on some engines).
  4.  

Use care in removing the keys; they are easily lost.

  1. Remove the valve seals from the intake valve guides. Throw these old seals away, as you'll be installing new seals during reassembly.
  2.  
  3. Slide the valves out of the head from the combustion chamber side.
  4.  



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Fig. Fig. 1: Use a valve spring compressor tool to relieve spring tension from the valve caps



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Fig. Fig. 2: A small magnet will help in removal of the valve keys



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Fig. Fig. 3: Be careful not to lose the valve keys

  1. Make a holder for the valves out of a piece of wood with drilled holes or cardboard. Make sure you number each hole in the holder to keep the valves in proper order. Slide the valve out of the head from the combustion chamber side; they MUST be installed in their original locations.
  2.  

To install:

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

To install the valve and rocker assembly:
  1. Lubricate the valve stems with clean engine oil.
  2.  
  3. Install the valves in the cylinder head, one at a time, as numbered.
  4.  



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Fig. Fig. 4: Once the spring has been removed, the O-ring may be removed from the valve stem



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Fig. Fig. 5: Invert the cylinder head and withdraw the valve from the cylinder head bore



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Fig. Fig. 6: Exploded view of the valve spring, retainer (cap) and seal assembly

  1. Lubricate and position the seals and valve springs, again a valve at a time.
  2.  
  3. Install the spring caps, and compress the springs.
  4.  
  5. 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.
  6.  
  7. Using needle nose 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.
  8.  
  9. Install the cylinder head(s).
  10.  

INSPECTION



See Figures 7, 8, 9, 10, 11, 12 and 13

Inspect the valve faces and seats (in the head) for pits, burned spots and other evidence of poor seating. If a valve face is in such bad shape that the head of the valve must be ground in order to true up the face, discard the valve because the sharp edge will run too hot. The correct angle for valve faces is 45 degrees. We recommend the refacing be done at a reputable machine shop.

Check the valve stem for scoring and burned spots. If not noticeably scored or damaged, clean the valve stem with solvent to remove all gum and varnish. Clean the valve guides using solvent and an expanding wire type valve guide cleaner. If you have access to a dial indicator for measuring valve stem-to-guide clearance, mount it so that the stem of the indicator is at 90 degrees to the valve stem, and is as close to the valve guide as possible. Move the valve off its seat, and measure the valve guide-to-stem clearance by rocking the stem back and forth to actuate the dial indicator. Measure the valve stems using a micrometer, and compare to specifications to determine whether stem or guide wear is responsible for the excess clearance. If a dial indicator and micrometer are not available to you, take your cylinder head and valves to a reputable machine shop of inspection.

Make sure the valve stem is not bent. The valve may be rolled on a flat surface such as a mirror or glass. An even better indication of valve stem bending can be determined by carefully chocking the stem into an electric drill. Use the drill the spin the stem while you watch the valve head. A bent stem will be obvious by the wobbling of the head. Be very careful if this method is used. If the valve stem is not properly chocked in position it could come flying out of the drill and cause injury.



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Fig. Fig. 7: A dial gauge may be used to check valve stem-to-guide clearance



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Fig. Fig. 8: Use a micrometer to measure the valve stem diameter



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Fig. Fig. 9: Valve stems may be rolled on a flat surface to check for bends

Some of the engines covered in this guide are equipped with valve rotators, which double as valve spring caps. In normal operation the rotators put a certain degree of wear on the tip of the valve stem; this ear appears as concentric rings on the stem tip. However, if the rotator is not working properly, the wear may appear as straight notches or X patterns across the valve stem tip. Whenever the valves are removed from the cylinder head, the tips should be inspected for improper pattern, which could indicate valve rotator problems. Valve stem tips will have to be ground flat if rotator patterns are severe.



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Fig. Fig. 10: Critical valve dimensions



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Fig. Fig. 11: When using a dial gauge to check stem-to-guide clearance, rock the stem back and forth a check the gauge readings



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Fig. Fig. 12: Valve stem wear patterns



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Fig. Fig. 13: Have the valve seat concentricity checked by a reputable machine shop

REFACING



This procedure should only be performed by a qualified machine shop.

 
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