Valve Seats

Fig 1: Valve Face and Seat

Courtesy of CHRYSLER LLC

1 - SEAT WIDTH

2 - FACE ANGLE

3 - SEAT ANGLE

4 - SEAT CONTACT AREA

When refacing valve seats, it is important that the correct size valve guide pilot be used for re-seating stones. A true and complete surface must be obtained.
Measure the concentricity of valve seat using dial indicator. Total runout should not exceed 0.051 mm (0.002 inch.) total indicator reading.
Inspect the valve seat (3) with Prussian blue to determine where the valve (1) contacts the seat. To do this, coat valve seat (1) 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 (2), contact is satisfactory. If the blue is transferred to top edge of valve face (2), then lower valve seat (3) with a 15° stone. If the blue is transferred to the bottom edge of valve face (2), then raise valve seat (3) with a 65° stone.
NOTE: Valve seats (1) which are worn or burned can be reworked, provided that correct angle and seat width (1) are maintained. Otherwise cylinder head must be replaced.
When seat is properly positioned the width of the intake seats should be 0.75 to 1.25 mm (0.0296 to 0.0493 in.) and exhaust seats should be 1.25 to 1.75 mm (0.049 to 0.069 in.) .