Refacing Valves And Valve Seats

To recondition or reface valve use a valve-refacing machine (available commercially). Adjust grinder to exactly the same angle as valve face, which is 45° for both intake and exhaust valves. Make very light cuts, being extremely careful to remove no more metal than is necessary to clean up and true valve face. Valve is correctly refaced when all pits are removed from valve face and face is concentric with stem. If end of valve stem shows uneven wear, true end of stem on a valve refacing grinder equipped with suitable attachment. If grinding leaves the edge of valve very thin or sharp, or indicates valve stem warpage, install a new valve. A valve in this condition does not seat normally and will burn easily.

Valve seats, like valves, are subject to wear, pitting and burning and should be refaced each time valves are refaced. Use an electric motor driven valve seat grinder (available commercially), for this operation. When refacing, be sure to maintain correct valve seat angle, seat width and relief diameter (see Fig. 3B-9). If the valve seat becomes too wide, grind the seat relief diameter to achieve specified seat width. Be careful that no more metal is removed than absolutely necessary to completely clean up and true valve seats.

If valve seats and valve faces have been smoothly and accurately refaced, very little lapping will be required to complete seating operation. Apply a touch of lapping compound to valve face, insert valve in guide, and using Lapping Tool, Part No. 96550-36, give valve a few oscillations - just enough to give face and seat a lapped finish (see Fig. 3B-10). Remove valve, wash valve face and seat thoroughly with clean gasoline and allow to dry, or blow dry with compressed air. When inspection shows an unbroken lapped finish around both valve face and seat, valve is well-seated. Apply a light coat of oil to valve face and seat when reconditioning job is finished.

0 0

Post a comment