Valve Seat: Service and Repair

Fig. 28 Contacting Width "W" & Seat Face Angle Of Valve:

Check valve seats for pitting at valve contact surfaces and reseat or replace if worn excessively. Before valve seat work is performed, ensure valve and valve guide are within specifications.
1. Bore out old seat until it collapses. Set machine to ensure that boring does not continue past bottom face of seat recess in cylinder head.
2. Ream cylinder head recess. Be sure to ream in circles concentric to valve guide center.
3. Oversize is 0.020 inches. Exhaust specification is 1.2874-1.2880 inches and intake is 1.4764-1.4770 inches.
4. Heat cylinder head to 230-266°F by soaking in heated oil.
5. Press fit valve seat until it seats on bottom.
6. Cut or grind valve seat outer diameter, using suitable tool, to 1.2905-1.2912 inches for exhaust valves and 1.4802-1.4808 inches for intake valves.
7. After cutting, lap seat with abrasive compound.
8. Check valve seating for face angle and contacting width "W", Fig. 28. Contacting width for intake valves is 0.0429-0.0516 inch and exhaust valve contacting width is 0.0508-0.0594 inches.