Valve Seat: Service and Repair

1. When refacing valve seats, it is important 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 and valve guide using a valve seat runout dial indicator. Total runout should not exceed 0.051 mm (0.002 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 the valve face, lower valve seat with a 15 degrees stone. If the blue is transferred to the bottom edge of valve face raise valve seat with a 65 degrees stone.
- Intake valve seat diameter is 33 mm (1.299 inch)
- Exhaust valve seat diameter is 28 mm (1.102 inch)
4. Valve seats which are worn or burned can be reworked, provided that correct angle and seat width are maintained. The intake valve seat must be serviced when the valve seat width is 2.0 mm (0.079 inch) or greater. The exhaust valve seat must be serviced when the valve seat width is 2.5 mm (0.098 inch) or greater. Otherwise the cylinder head must be replaced.





5. When seat is properly positioned the width of intake and exhaust seats should be 0.75 - 1.25 mm (0.030 - 0.049 inch).





6. Check valve tip to spring seat dimensions A after grinding the valve seats or faces. Grind valve tip to 43.51 - 44.57 mm (1.71 - 1.75 inch) for exhaust valve and 45.01 - 46.07 mm (1.77 - 1.81 inch) for intake valve over spring seat when installed in the head. The valve tip chamfer may need to be reground to prevent seal damage when the valve is installed.