VALVE RECONDITIONING CONTINUED
Refacing Valve Seats and Seat Inserts
1. Remove all carbon, scale, and oil before attempting to reface valve seats. Grinding stone, when placed against
an oily seat, will become fouled and uneven grinding will occur.
2. Use a clean, oiled rag to lubricate pilot shank lightly. Before installing pilot, be certain that valve guides are
perfectly clean. This is important to prevent an eccentric cut to seat.
3. Depress stone to correct angle and install a pilot of correct size in valve guide bore (see Intake and Exhaust
Valve Specifications in this work package) for seat angle and guide ID.
4. Lower grinder head over pilot shank until stone just clears valve seat (Figure 18). Turn on power and very
gently allow stone to contact valve seat. Very little pressure other than normal weight of stone must be used.
Sudden, hard pressures can cause cocking of pilot in guide and result in eccentric grinding. Frequently raise
stone from valve seat in order to prevent overheating and to clear away grinding dust. Grind seat sufficiently to
provide an even, smooth surface.
Figure 18. Grinding Valve Seat.