Seat Refacing

CAUTION: The interference angle of the valve and seat should not be lapped out. Remove all grooves or score marks from the end of the valve stem and chamfer it as necessary. Do not remove more than 0.254 mm (0.010 inch) from the end of the valve stem. Failure to follow these procedures may result in a non-usable valve.

NOTE: If the valve face runout is excessive and/or it is necessary to remove pits and grooves, reface the valves to a true 45-degree angle. Remove only enough stock to correct the runout or to clean up the pits and grooves. If the edge of the valve head is less than 0.794 mm (1/32 inch) thick after grinding, replace the valve as the valve will run too hot in the engine.

Measure the valve seat width. Reface the valve seats if the width is not within specifications.

Refer to Engine Service in the Rotunda Tool catalog for a description of the various valve seat grinders and cutters available.

Refacing of the valve seat should be closely coordinated with the refacing of the valve face so that the finished seat and valve face will be concentric and the specified interference angle will be maintained. This is important so that the valve and seat will have a compression-tight fit. Make sure refacer grinding wheels are properly dressed.

The finished valve seat should contact the approximate center of the valve face. Determine where the valve seat contacts the face.

To do this, coat the seat with Prussian Blue and set the valve in place. Rotate the valve with light pressure. if the blue is transferred to the center of the valve face, the contact is satisfactory. If the blue is transferred to the top edge of the valve face, lower the valve seat. If the blue is transferred to the bottom edge of the valve face, raise the valve seat.

Grind the valve seats to a true 45-degree angle. Remove only enough stock to clean up pits and grooves or to correct the valve seat runout. After the seat has been refaced, measure valve seat contact width.