Valve Seat: Service and Repair

CAUTION: Valve seats are released for service and can be replaced. Damaged seats are usually replaced by a machine shop.





1. Using a 45 degree carbide cutter or proper stone, resurface the valve seats. Remove only enough metal to clean the seats. Check the valve seat width:





2. Check the valve seating position. Apply a thin coat of Prussian blue (or white lead) to the valve face. Install the valve. While applying light pressure to the valve, rotate the valve against the seat.





3. Check the valve face and seat for the following:
^ If blue appears 360 degrees around the face, the valve is concentric. If not, replace the valve.
^ If blue appears 360 degrees around the valve seat, the guide and seat are concentric. If not, grind the seat.
^ Check that the seat contact is on the middle of the valve face. If not, correct the valve seat as follows:





^ If the seating is too high on the valve face, use 30 degree and 45 degree cutters or stones to correct the seat width.





^ If the seating is too low on the valve face, use 60 degree and 45 degree cutters or stones to correct the seat.





4. Hand-lap the valve and valve seat with an abrasive compound.
5. Clean the valve and valve seat after hand-lapping using solvent.





6. Install the valve without seal and measure the tip height with calipers.