AMC Coupes/Sedans/Wagons 1975-1988 Repair Information

Valves and Springs

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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 V8 models). Also note that the valve keys, rotators, caps, etc. should be arranged in a manner which will allow you to install them on the valve on which they were originally used.

REMOVAL 4-121 Engine



See Figures 1 through 7

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Fig. Fig. 1: Fabricate a cylinder head fixture and attach it to the of the head4-121 engine



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Fig. Fig. 2: Use a valve spring compressor tool to relieve spring tension from the valve caps



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Fig. Fig. 3: A magnet may be helpful in removing the valve keepers



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Fig. Fig. 4: Be careful not to lose the valve keepers



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Fig. Fig. 5: Remove the spring from the valve stem in order to access the seal



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Fig. Fig. 6: Remove the valve stem seal from the cylinder head



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Fig. Fig. 7: Invert the cylinder head and withdraw the valve from the cylinder head bore

  1. Remove the cylinder head.
  2.  
  3. Make a wooden fixture according to the dimensions shown in the accompanying illustration. Attach the fixture to the bottom of the head with 3 / 8 in. X 3 / 4 in. (10mm X 83mm) bolts and nuts, to hold the valves against their seats while the valve springs are compressed.
  4.  
  5. Remove the camshaft from the head.
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  7. Loosely install a nut to one camshaft bearing stud next to each valve.
  8.  
  9. Lift the tappets from their bores, keeping them in order for installation.
  10.  
  11. Place a 21mm deep socket on each retainer and strike it sharply with a hammer to loosen the valve locks.
  12.  
  13. Using spring compressor J-26809, compress the valve springs. Remove the locks, retainers, springs and oil deflectors.
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  15. When all of the parts are removed from all the valves, remove the home made retaining tool and remove the valves. Keep them in order for installation.
  16.  

Except 4-121 Engine

  1. The head must be removed from the engine.
  2.  
  3. Remove the rocker arm assemblies.
  4.  
  5. Using a spring compressor, compress the valve springs and remove the keepers (locks). Relax the compressor and remove the washers or rotators, the springs, and the lower washers (on some engines). Keep all parts in order.
  6.  

INSPECTION and REFACING



See Figures 8 through 12



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Fig. Fig. 8: Check the valve stem-to-guide clearance using a dial indicator



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Fig. Fig. 9: A wire wheel may be used to clean the combustion chambers of carbon deposits



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Fig. Fig. 10: A dial gauge may be used to check valve stem-to-guide clearance



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Fig. Fig. 11: Valve stems may be rolled on a flat surface to check for bends



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Fig. Fig. 12: Use a micrometer to check the valve stem diameter

  1. Clean the valves with a wire wheel.
  2.  
  3. Inspect the valves for warping, cracks or wear.
  4.  
  5. The valves may be refaced if not worn or pitted excessively.
  6.  
  7. Using a valve guide cleaner chucked into a drill, clean all of the valve guides. Check the valve stem diameter and the guide diameter with micrometers. The guide must be reamed and an insert pressed in, or they may be knurled to bring up interior metal, restoring their diameter. Oversized valve stems are available to compensate for wear.
  8.  

AMC recommends that, if the 4-121 guides are worn excessively, the head should be replaced. Inserts are not available.

  1. Install each valve into its respective port (guide) of the cylinder head.
  2.  

  1. Mount a dial indicator so that the stem is at 90° to the valve stem, as close to the valve guide as possible.
  2.  
  3. 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.
  4.  
  5. In short, the refacing of valves and other such head work is most easily done at a machine shop. The quality and time saved easily justifies the cost.
  6.  
  7. Inspect the springs for obvious signs of wear. Check their installed height and tension using the values in the Valve Specifications Chart in this section.
  8.  

REFACING



See Figures 13 through 17



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Fig. Fig. 13: Typical critical valve dimensions



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Fig. Fig. 14: Valve grinding is usually performed with a machine



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Fig. Fig. 15: Sectional view of incorrect and correct valve seat width and centering



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Fig. Fig. 16: Use a dial gauge to check the valve seat concentricity



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Fig. Fig. 17: A hand reamer may be used on the valve seats


CAUTION
On the 4-121, reface only the intake valves. Never attempt to reface the exhaust valves. Exhaust valves are sodium filled and refacing could be hazardous! When refacing the intake valves, the face width should not exceed 3.5mm.

Using a valve grinder, resurface the valves according to specifications in this information. 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 1 / 32 in. (0.79375mm) 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 or cam.

LAPPING



See Figures 18 and 19



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Fig. Fig. 18: Lapping the valves by hand



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Fig. Fig. 19: A homemade valve lapping tool can be fabricated

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 your palms, changing position and lifting the tool often to prevent grooving.
  2.  
  3. Lap the valve until a smooth, polished seat is evident.
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  5. Remove the valve and tool, and rinse away all traces of grinding compound.
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VALVE SPRING TESTING



See Figures 20, 21, 22 and 23



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Fig. Fig. 20: Use a caliper gauge to check the valve spring free-length



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Fig. Fig. 21: Check the valve spring for squareness on a flat service; a carpenter's square can be used



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Fig. Fig. 22: A carpenters square may be used to check the spring free length and squareness



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Fig. Fig. 23: Check the valve spring installed height using a spring testing tool

Place the spring on a flat surface next to a square. Measure the height of the spring, and rotate it against the edge of the square to measure distortion. If spring height varies (by comparison) by more than 1 / 16 in. (1.5875mm) or if distortion exceeds 1 / 16 in. (1.5875mm), replace the spring.In addition to evaluating the spring as above, test the spring pressure at the installed and compressed (installed height minus valve lift) height using a valve spring tester. Spring pressure should be ± 1 lb. of all other springs in either position.

INSTALLATION



  1. Coat all parts with clean engine oil. Install all parts in their respective locations. The spring is installed with the closely wound coils toward the valve head. Always use new valve seals.
  2.  
  3. Use a spring compressor to install the keepers and slowly release the compressor after the keepers are in place.
  4.  
  5. Release the spring compressor. Tap the end of the stem with a wood mallet to insure that the keepers are securely in place.
  6.  
  7. Install all other parts in reverse order of removal.
  8.  

 
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