Jeep Wrangler/YJ 1987-1995 Repair Guide

Valves and Springs

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See Figure 1



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Fig. Fig. 1: Valve and valve components

Fabricate a valve arrangement board to use when you remove the valves, which will indicate the port in which each valve was originally installed. 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



See Figures 2 and 3



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Fig. Fig. 2: Using a lever-type valve spring compressor tool. With the retainer and spring compressed, the valve locks can be removed



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Fig. Fig. 3: Using a screw-type valve spring compressor tool

  1. Remove the cylinder head 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, then remove the washers or retainers, the springs and, if equipped, the lower washers. Keep all parts in order.
  6.  

CLEANING AND INSPECTION



See Figures 4, 5, 6, 7 and 8

  1. Clean the valves with a wire wheel, then inspect the valves for warping, cracks or wear. They may be refaced if not excessively worn or pitted.
  2.  
  3. Using a guide cleaner chucked into a drill, clean the valve guides. Check the valve stem and guide diameters with micrometers. The guides are not replaceable. If out of specification, they must be reamed and an insert pressed in, or they may be knurled to bring up interior metal, restoring their diameter.
  4.  



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Fig. Fig. 4: Measurement of the valve guide bore diameter



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Fig. Fig. 5: Measurement of the lateral movement of the valve stem



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Fig. Fig. 6: Measurement of the valve seat run-out



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Fig. Fig. 7: Valve facing margin



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Fig. Fig. 8: Critical valve dimensions

Valves with oversized stems are normally available to compensate for wear.

  1. Install each valve into its respective port (guide) of the cylinder head.
  2.  
  3. Mount a dial indicator so that its pointer is at 90º to the valve stem, as close to the valve guide as possible.
  4.  
  5. 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.
  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 of valves and other such cylinder head work is most easily done at a machine shop. The quality and time saved easily justifies the cost.

REFACING



See Figure 9

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

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

A minimum margin of 1 / 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 or cam.



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Fig. Fig. 9: Refacing a valve. A well equipped machine shop can do this job

LAPPING



See Figures 10 and 11

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.
  4.  
  5. Remove the valve and tool, and rinse away all traces of grinding compound.
  6.  



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Fig. Fig. 10: Lapping the valves by hand



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Fig. Fig. 11: Homemade valve lapping tool

VALVE SPRING TESTING



See Figures 12, 13 and 14

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 more than 1 / 16 in. (1.6mm), or if distortion exceeds 1 / 16 in. (1.6mm), replace the spring.

In addition these evaluations, check spring pressure at both the installed and compressed heights using a valve spring tester.

Compressed height is the installed height minus the valve lift measurement.

Spring pressure should be within 1 lb. of all other springs in either position.



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Fig. Fig. 12: Check the valve spring free length and squareness



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Fig. Fig. 13: Testing the valve spring



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Fig. Fig. 14: Valve spring installed height (A)

INSTALLATION



See Figure 15



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Fig. Fig. 15: Install the valve stem seals

  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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