Valve Grinding and Valve Guide Inspection and Replacement

Tools Required

• J 37968  Valve Guide Seal Installer Kit
• J 37971  Reamer

Fig 1: Measuring Inside Diameter Of Guide Bushing
Courtesy of GENERAL MOTORS CORP.
1. Use a dial hole gage and measure the inside diameter of the valve guide bushing.

   Standard Valve Guide Bushing Inside Diameter:  5.500-5.518 mm (0.2165-0.2172 in)

Fig 2: Measuring Outside Diameter Of Valve Stem
Courtesy of GENERAL MOTORS CORP.
2. Use a micrometer and measure the outside diameter of the valve stem.
   • Standard Intake Valve Stem Diameter:  5.460-5.475 mm (0.21496-0.21555 in)
   • Standard Exhaust Valve Stem Diameter:  5.445-5.470 mm (0.21437-0.21535 in)
3. To obtain the valve guide bushing oil clearance, subtract the valve stem outside diameter measurement from the valve guide bushing inside diameter measurement.
   • Standard Intake Valve Oil Clearance:  0.025-0.058 mm (0.0010-0.0023 in)
   • Maximum Intake Valve Oil Clearance:  0.08 mm (0.0031 in)
   • Standard Exhaust Valve Oil Clearance:  0.030-0.073 mm (0.0012-0.0029 in)
   • Maximum Exhaust Valve Oil Clearance:  0.10 mm (0.0039 in)
4. If the clearance is greater than the maximum specified, replace the valve and the valve guide bushing.
Fig 3: Heating Cylinder Head
Courtesy of GENERAL MOTORS CORP.
5. Gradually heat the cylinder head to 80-100° C (176-212° F)
Fig 4: Removing Valve Guide Bushing
Courtesy of GENERAL MOTORS CORP.
6. Use a J 37968  and a hammer and tap out the valve guide bushing.
Fig 5: Measuring Bushing Bore Diameter Of Cylinder Head
Courtesy of GENERAL MOTORS CORP.
7. Use a dial hole gage and measure the bushing bore diameter of the cylinder head.
8. Select a new valve guide bushing (standard or oversize).
9. If the bushing bore diameter of the cylinder head is greater than 10.506 mm (0.4136 in), machine the bushing bore to specifications.

   Valve Guide Bushing Bore Diameter:  10.538-10.556 mm (0.4149-0.4156 in)

10. If the bushing bore diameter of the cylinder head is greater than 10.556 mm (0.4156 in), replace the cylinder head.
IMPORTANT: Pay close attention when replacing the valve guide bushings and ensure that the proper valve guide bushing is used.
11. Measure the intake and exhaust valve guide bushings. The intake valve guide bushings are shorter than the exhaust valve guide bushings.
Fig 6: Heating Cylinder Head
Courtesy of GENERAL MOTORS CORP.
12. Gradually heat the cylinder head to 80-100° C (176-212° F).
Fig 7: Installing Valve Guide Bushing
Courtesy of GENERAL MOTORS CORP.
13. Use a J 37968  and a hammer and tap the new valve guide bushing into the cylinder head.
14. Install the valve guide bushing to the specified protrusion height of 15.3-15.7 mm (0.602-0.618 in).
Fig 8: Reaming Valve Guide Bushing
Courtesy of GENERAL MOTORS CORP.
15. Use a J 37971  and ream the valve guide bushing to obtain the standard specified clearance between the valve guide bushing and valve stem.
    • Standard Intake Valve Oil Clearance:  0.025-0.058 mm (0.0010-0.0023 in)
    • Standard Exhaust Valve Oil Clearance:  0.030-0.073 mm (0.0012-0.0029 in)
IMPORTANT: Proper reconditioning of the valve seats is very important. Because the valve guide serves to support and center the valve grinder, it is essential that the valve guide is cleaned properly. If the valve guide requires reaming, this must be done first.
16. Use the following as a general guideline when reconditioning the cylinder head.
    • Recondition the valve seat after reaming the valve guide bores.
    • Inspect the valve seats for excessive wear and burned spots. Valve seats may be reconditioned by grinding. Using a 45 degree carbide cutter, resurface the valve seat. Remove only enough metal to clean the seat.
    • Measure the residuary width of the valve seat.
    • Minimum Intake Residuary Length:  3.3 mm (0.130 in)
    • Minimum Exhaust Residuary Length:  3.2 mm (0.126 in)
    • Replace the cylinder head if the residuary width is less than minimum.
    • The valves must seat perfectly for the engine to deliver optimum power and performance.
    • Cooling the valve heads is another important factor. Good contact between each valve and its seat in the cylinder head is necessary to insure that the heat in the valve head is properly carried away.
    • Regardless of what type of equipment is used, it is essential that the valve guide bores are free from carbon or dirt to ensure the proper centering of the pilot in the guide.