GM Prizm/Nova 1985-1993 Repair Guide

Valve Guides

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See Figure 1

INSPECTION



Valve guides should be cleaned as outlined earlier and checked when the stem-to-guide clearance is measured. As a general rule, if the engine admits oil through the guides (and the oil seals are in good condition), the guides are worn.

Valve guides which are not excessively worn or distorted may, in some cases, be knurled rather than replaced. Knurling is a process in which metal inside the valve guide is displaced and raised by a cutter, making a very fine crosshatched pattern. This raised pattern reduces the clearance to the valve stem and provides excellent oil control. The possibility of knurling rather than replacing the valve guides should be discussed with a machinist.



Click image to see an enlarged view

Fig. Fig. 1: Cross-section of a knurled valve guide

REMOVAL & INSTALLATION



See Figures 2, 3 and 4


CAUTION
Replacing the valve guides requires heating the head to high temperatures and the use of special tools. Do not attempt this repair if you are not equipped with the proper heating and handling equipment. Do not attempt this repair unless equipped with the correct valve guide tools and a reamer.When handling the heated head, always use heavy gloves and tongs.

1985-88 VIN Code 4 Engine
  1. Heat the cylinder head evenly to 194°F.
  2.  
  3. Carefully remove the head from the heat source and support it upright on the workbench.
  4.  
  5. Using valve guide tool such as J-25367-1 or similar, and a hammer, drive the guide out of the head.
  6.  
  7. Reheat the head to 194°F (90°C) and support it on the workbench.
  8.  
  9. Use the guide tool and a hammer to drive in the new guide until it projects 14.5-15.0mm.
  10.  



Click image to see an enlarged view

Fig. Fig. 2: Correct installation of guides. GM special tool shown - 1985-88 VIN Code 4 engine

  1. Allow the head and guide to air cool. Do not attempt to quick-cool the metal with any water or fluid.
  2.  
  3. Measure the inner diameter of the guide. Compare this to the stem diameter of the new valve. If the stem to guide clearance is insufficient, ream the new guide with a sharp 7mm reamer until the correct clearance is obtained.
  4.  

1988 VIN Code 5 Engine
  1. Break off the upper part of the old bushing. Wrap an old valve stem in tape to prevent the stem from dropping too far into the guide. Pad the surrounding area with rags. Insert the old valve into the guide and strike the valve with a hammer.
  2.  


WARNING
Be careful not to damage the surrounding area in which the lifter sits.



Click image to see an enlarged view

Fig. Fig. 3: A quick and handy method for breaking off the tops of valve guides before removal - 1985-88 VIN Code 4 engine

  1. Heat the cylinder head gradually, in water, to 212°F.
  2.  
  3. Carefully remove the head from the water. Use tool J-37133 or similar and a hammer to drive out the guide.
  4.  
  5. With the guide removed, measure the bore (in the head) into which the guide fits. If the bore is greater than 10.9mm, have the bore ground to 11.05-11.08mm and install a 0.05mm oversize guide. If the bore is greater than 11.08mm, the head must be replaced.
  6.  
  7. Reheat the head in water to 212°F (100°C), then carefully remove it from the water.
  8.  
  9. Using the removal and installation tool (J-37133), drive in the new guide until the snapring makes contact with the cylinder head.
  10.  
  11. Measure the inner diameter of the guide. Compare this to the stem diameter of the new valve. If the stem to guide clearance is insufficient, ream the new guide with a sharp 6mm reamer until the correct clearance is obtained.
  12.  

1989-90 VIN Code 6 Engine 1991-92 VIN Code 5 Engine
  1. Gradually heat the cylinder head to 212°F.
  2.  
  3. Carefully remove the head from the heat source.
  4.  
  5. Using tool J-37133 or similar and a hammer to drive out the guide.
  6.  
  7. With the guide removed, measure the bore (in the head) into which the guide fits. If the bore is greater than 10.9mm, have the bore ground to 11.05-11.08mm and install a 0.05mm oversize guide. If the bore is greater than 11.08mm, the head must be replaced.
  8.  
  9. Reheat the head to 212°F (100°C) and then remove it from the heat.
  10.  
  11. Using the REMOVAL & INSTALLATION tool (J-37133) and an adapter such as J 38277, drive in the new guide until it projects 12.5-13.0mm above the head.
  12.  
  13. Measure the inner diameter of the guide. Compare this to the stem diameter of the new valve. If the stem to guide clearance is insufficient, ream the new guide with a sharp 6mm reamer until the correct clearance is obtained.
  14.  



Click image to see an enlarged view

Fig. Fig. 4: Use a precision reamer to enlarge new valve guides if necessary

1990 VIN Code 5 Engine 1991-92 VIN Code 6 Engine
  1. Using tool J-37133 or similar and a hammer to drive out the guide.
  2.  
  3. With the guide removed, measure the bore (in the head) into which the guide fits. If the bore is greater than 11.027 mm, have the bore ground to 11.05-11.08mm and install a 0.05mm oversize guide. If the bore is greater than 11.08mm, the head must be replaced.
  4.  
  5. Using the removal and installation tool (J-37133).
  6.  
  7. Measure the inner diameter of the guide. Compare this to the stem diameter of the new valve. If the stem to guide clearance is insufficient, ream the new guide with a sharp 6mm reamer until the correct clearance is obtained.
  8.  

1993
  1. Using tool J-37133 or similar and a hammer to drive out the guide.
  2.  
  3. With the guide removed, measure the bore (in the head) into which the guide fits. If the bore is greater than 11.27mm, have the bore ground to 11.05-11.077mm and install a 0.05mm oversize guide. If the bore is greater than 11.077mm, the head must be replaced.
  4.  
  5. Using the removal and installation tool (J-37133) and an adapter such as J 38277, drive in the new guide until it projects 12.7-13.1mm above the head.
  6.  
  7. Measure the inner diameter of the guide. Compare this to the stem diameter of the new valve. If the stem to guide clearance is insufficient, ream the new guide with a sharp 6mm reamer until the correct clearance is obtained.
  8.  

 
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