Tools Required

1. Use a dial hole gauge and measure the inside diameter of the valve guide bushing.

Standard Valve Guide Bushing Inside Diameter
5.510-5.530 mm (0.2169-0.2177 in)




2. Use a micrometer and measure the outside diameter of the valve stem.

Standard Intake Valve Stem Diameter
5.470-5.485 mm (0.2154-0.2159 in)

Standard Exhaust Valve Stem Diameter
5.465-5.480 mm (0.2152-0.2157 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
0.025-0.060 mm (0.0010-0.0024 in)

Maximum Intake Valve Oil Clearance
0.08 mm (0.0031 in)

Standard Exhaust Valve Oil Clearance
0.030-0.065 mm (0.0012-0.0026 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.



5. Gradually heat the cylinder head to 80-90°C (176-212°F)



6. Use a J 37968 and a hammer and tap out the valve guide bushing.



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 10.306 mm (0.4057 in), machine the bushing bore to specifications.

Valve Guide Bushing Bore Diameter
10.335-10.356 mm (0.4068-0.4077 in)

10. If the bushing bore diameter of the cylinder head is greater than 10.356 mm (0.4077 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 (1) are shorter than the exhaust valve guide bushings (2).



12. Gradually heat the cylinder head to 80-90°C (176-212°F).



13. Use aJ 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 8.7-9.1 mm (0.342-0.358 in).



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
0.025-0.060 mm (0.0010-0.0024 in)

Standard Exhaust Valve Oil Clearance
0.030-0.065 mm (0.0012-0.0026 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. If grinding results in the new seat being too wide it may be narrowed by using a 20 degree or 70 degree stone. The 20 degree stone will lower the seat and the 70 degree stone will raise the seat.

•	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.

•	The valve seats should be concentric to within 0.05 mm (0.031 in) total indicator reading.

•	Replace any valve that is not in serviceable condition.