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 cutters available.

Reconditioning of valve seat should be closely coordinated with refacing of valve so that finished seat and valve face will be concentric and specified angle will be maintained. This is important so that valve and seat will have a compression-tight fit.





1. Select proper-size pilot and insert it into finished valve guide. Using the 75-degree cutter, make a light cut until a clean line can be seen all the way around bottom of seat angle.
2. Once this is done, use the 30-degree cutter until there is a clean line all the way around top of seat.
3. Then use the 45-degree cutter until seat is clean, free from pits and has an even width all the way around.
4. Check seat location and width by coating face of freshly refaced valve with Prussian Blue and set valve in place. With light pressure on valve head, turn valve one-quarter turn and remove.
5. Wipe Prussian Blue from valve and put it back in place.
6. With light pressure on valve, turn it one-quarter turn and remove. Do not touch valve face when removing. Look at valve face. There should be a line of blue about one-third of the way down face from margin, all the way around valve face.
7. If line is not in proper position, take the following steps:
a. If line is too close to margin, use the 30-degree cutter to lower top edge of seat.
b. If line is too far from margin, use the 45-degree cutter to raise top edge of seat.