GM Celebrity/Century/Ciera/6000 1982-1996 Repair Guide

Valves and Springs

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ADJUSTMENT



This procedure must be performed on V6 engines anytime the rocker arms have been loosened or removed.

  1. Remove the valve cover and the No. 1 spark plug.
  2.  
  3. Rotate the engine until the 0 mark on the crankshaft pulley aligns with the timing tab and the No. 1 cylinder is on the TDC of the compression stroke.
  4.  
  5. With the engine in this position, adjust the exhaust valves of No. 1, 2 and 3 and the intake valves of No. 1, 5 and 6. Back out the adjusting nut until lash is felt at the pushrod, then turn the nut to remove the lash. With the lash removed, turn the nut an additional 1 1 / 2 turns.
  6.  
  7. Rotate the engine 1 complete revolution until the 0 mark on the crankshaft pulley aligns with the timing tab and the No. 4 piston is on the TDC of the compression stroke.
  8.  
  9. With the engine in this position, adjust the exhaust valves of No. 2, 3 and 4; adjust the valves the same way as in Step No. 3.
  10.  
  11. Install the valve covers and the spark plugs.
  12.  

REMOVAL & INSTALLATION



See Figures 1 and 2

  1. Remove the cylinder head(s) from the vehicle as previously outlined.
  2.  
  3. Using a suitable valve spring compressor, compress the valve spring and remove the valve keys using a magnetic retrieval tool.
  4.  



Click image to see an enlarged view

Fig. Fig. 1: A small magnet will help in removal of the valve keys

  1. Slowly release the compressor and remove the valve spring caps (or rotators) and the valve springs.
  2.  



Click image to see an enlarged view

Fig. Fig. 2: Once the spring has been removed, the O-ring may be removed from the valve stem

  1. Fabricate a valve arrangement board to use when you remove the valves, which will indicate the port in which each valve was originally installed (and which cylinder head on V6 models). Also note that the valve keys, rotators, caps, etc. should be arranged in a manner which will allow you to reinstall them on the valve on which they were originally used.
  2.  
  3. Remove and discard the valve seals. On models using the umbrella type seals, note the location of the large and small seals for assembly purposes.
  4.  
  5. Thoroughly clean the valves on the wire wheel of a bench grinder, then clean the cylinder head mating surface. Avoid using a metallic scraper, since this can cause damage to the cylinder head mating surface, especially on models with aluminum heads.
  6.  
  7. Using a valve guide cleaner chucked into a drill, clean all of the valve guides.
  8.  

To install:
  1. Lubricate all of the valve stems with a light coating of engine oil, then install the valves into the proper ports/guides.
  2.  
  3. Install the valve seals. Be sure to use a seal protector to prevent damage to the seals as they are pushed over the valve keeper grooves. Install O-ring seals in the second groove closest to the head.
  4.  
  5. Install the valve springs and the spring retainers (or rotators), and using the valve compressing tool, compress the springs.
  6.  
  7. After all of the valves are installed and retained, tap each valve spring retainer with a rubber mallet to seat the keepers in the retainer.
  8.  

INSPECTION



See Figures 3, 4 and 5

  1. Reinstall each valve into its respective port (guide) of the cylinder head.
  2.  
  3. Mount a dial indicator so that the stem is at 90° to the valve stem, as close to the valve guide as possible.
  4.  



Click image to see an enlarged view

Fig. Fig. 3: A dial gauge may be used to check valve stem-to-guide clearance

  1. 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.
  2.  
  3. Measure the valve stems using a micrometer, and compare to specifications, to determine whether stem or guide wear is responsible for excessive clearance.
  4.  



Click image to see an enlarged view

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



Click image to see an enlarged view

Fig. Fig. 5: Valve stems may be rolled on a flat surface to check for bends

REFACING



Using a valve grinder, resurface the valves according to specifications in this section. All machine work should be performed by a competent, professional machine shop.

Valve face angle is not always identical to valve seat angle.

A minimum margin of 3 / 32 in. (0.8mm) should remain after grinding the valve. The valve stem top should also be squared and resurfaced, by placing the stem in the V-block of the grinder, and turning it while pressing lightly against the grinding wheel. Be sure to chamfer the edge of the tip so that the squared edges don't dig into the rocker arm.

LAPPING



This procedure should be performed after the valves and seats have been machined, to insure that each valve mates to each seat precisely.

  1. Invert the cylinder head, lightly lubricate the valve stems, and install the valves in the head as numbered.
  2.  
  3. Coat valve seats with fine grinding compound, and attach the lapping tool suction cup to a valve head.
  4.  

Moisten the suction cup.

  1. Rotate the tool between the palms, changing position and lifting the tool often to prevent grooving.
  2.  
  3. Lap the valve until a smooth, polished seat is evident.
  4.  
  5. Remove the valve and tool, and rinse away all traces of grinding compound.
  6.  

 
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