Refacing Valves & Seats

REFACING VALVES AND VALVE SEATS
1. The intake and exhaust valve seats and valve face have a 45° angle.





Fig. 65

2. Inspect the remaining margin after the valves are refaced (Fig. 65). Intake valves with less than 0.95 mm (1/32 inch) margin and exhaust valves with less than 1.05 mm (3/64 inch) margin should be discarded.
3. 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. For specifications.
4. 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).
5. Inspect the valve seat with Prussian blue to determine where the valve contacts the seat. fib 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° stone.
6. 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.





Fig. 66

7. When seat is properly positioned the width of intake and exhaust seats should be 0.75 - 1.25 mm (0.030 - 0.049 inch) (Fig. 66).





Fig. 67

8. Check valve tip to spring seat dimensions A after grinding the valve seats or faces. Grind valve tip until within specifications. Measure from valve tip to spring seat when installed in the head (measurement A) (Fig. 67). Refer to Specifications. The valve tip chamfer may need to be reground to prevent seal damage when the valve is installed.