ISUZU Amigo/Pick-ups/Rodeo/Trooper 1981-1996

Valve Guides

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REMOVAL & INSTALLATION



Except Diesel Engine

See Figures 1, 2 and 3



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Fig. Fig. 1: Reaming the valve guide to restore clearance. Excessive valve-to-guide clearance can case valve guide, cylinder head or piston damage



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Fig. Fig. 2: Stem-to-guide clearance must be checked before and after valve guide service. Insufficient valve to guide clearance can case valve, guide or head damage



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Fig. Fig. 3: This cutaway view of a knurled valve guide resembles bolt threads

Most engines use integral valve guides; that is, they are a part of the cylinder head and cannot be replaced. The guides can, however, be reamed oversize if they are found to be worn past an acceptable limit. The reaming or knurling process should be performed by a qualified machine shop. Occasionally, a valve guide bore will be oversize as manufactured. These are marked on the inboard side of the cylinder heads on the machined surface just above the intake manifold.

If the guides must be reamed (this service is available at most machine shops) then valves with oversize stems must be fitted. Valves are usually available in 0.001 in., 0.003 in. and 0.005 in. stem oversizes for most applications. Valve guides which are not excessively worn or distorted may, in some cases, be knurled rather than reamed.

If the valve guides are worn, check with the machine shop. There are procedures for replacing or repairing the head. The procedures may involve reaming, knurling or cutting the heads to install replacement guides. Most of these procedures require new valves to be installed. But the cylinder head itself can be saved.

Diesel Engine

See Figures 2, 4 and 5



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Fig. Fig. 4: Valve guide removal-diesel engine



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Fig. Fig. 5: Valve guide installation-diesel engine

The following procedures requires the use of Valve Guide Removal and Installation tool No. J-26512 or equivalent.

  1. Insert a guide remover such as tool No. J-26512 or equivalent, into the guide from the combustion chamber side. Drive the guide upward and out. Remove the lower valve spring seat.
  2.  
  3. Apply clean engine oil to the outside of the new guide and position it on the head top-side. Using opposite side of the tool No. J-26512 or equivalent, drive the guide in until it bottoms.
  4.  

If the guides are replaced, the valves should be replaced also.

  1. The guide should protrude 0.4724 in. (12mm) above the head surface. Grind the end of the guide to achieve this height. Make certain that the guide has bottomed before grinding.
  2.  

KNURLING



See Figure 3

Valve guides which are not excessively worn or distorted may, in some cases, be knurled. Knurling is a process by which the metal on the valve guide bore is displaced and raised, thereby reducing clearance. Knurling also provides excellent oil control. The option of knurling rather than reaming valve guides should be discussed with a reputable machinist or engine specialist.

 
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