Valve Seat: Service and Repair

VALVE SEATS


CAUTION: Do not un-shroud valves during valve seat refacing.

1. When refacing valve seats, it is important that the correct size valve guide pilot be used for reseating stones. A true and complete surface must be obtained.
2. Measure the concentricity of valve seat using dial indicator No.13725. Total runout should not exceed .051 mm (.002 inch) total indicator reading.
3. Inspect the valve seat with Prussian blue to determine where the valve contacts the seat. To do this, coat valve seat LIGHTLY with Prussian blue then set valve in place. Rotate the valve with light pressure. If the blue is transferred to the center of valve face, contact is satisfactory. If the blue is transferred to top edge of valve face,lower valve seat with a 30 degree stone. If the blue is transferred to the bottom edge of valve face raise valve seat with a 75 degrees stone.

Note: Valve seats which are worn or burned can be reworked, provided that correct angle and seat width are maintained. Otherwise cylinder head must be replaced.






4. When seat is properly positioned the width of both seats should be 1.02 to 1.52 mm (0.040 to 0.060 inches.).







5. Check the valve tip height (A) and valve spring installed height (B) after refacing the valve and seats.