Valve Guide: Service and Repair

GUIDE REAMING
1. Ream the valve guides for oversize valves if the clearance exceeds the specifications.
2. Ream the valve guide bores for the oversize valves as necessary.
3. Reconditioning the valve seats is very important. Recondition valve seat after reaming the valve guide bores.
^ 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 inch) total indicator reading.
^ Reface pitted valves on a valve refacing machine in order to insure the correct relationship between the head and the stem.
^ Replace the valve is the stem is warped, or if the stem shows signs of excessive wear.
^ Replace the valve if the thickness at the edge of the head (margin) is less than the minimum margin specification.
^ Several different types of equipment are available for reconditioning valves and valve seats. Follow manufacturers recommendations for proper use to obtain the correct results.