Valve Seat: Service and Repair

Valve seats, refacing

CAUTION!

- When refacing valve seats, remove only enough material to produce the correct seat contact pattern. The maximum permissible refacing dimension must be calculated before refacing.
- If the maximum refacing dimension is exceeded, the hydraulic lifters will not function properly and the cylinder head must be replaced.

Calculating maximum permissible reworking dimension

- Insert valve and push firmly against valve seat.






- Measure distance -a- between center of valve stem and upper edge of cylinder head.

- Measured distance minus the minimum dimension is the maximum permissible refacing dimension.

Minimum dimensions:

- Intake valve: 33.8 mm (1.330 in.)

- Exhaustvalve: 34.1 mm (1.342 in.)

Example:






Note:

- If the measured distance -a- is smaller than the minimum dimension, measure again with new valves. If necessary, use shorter valves, or replace cylinder head.

Intake valve seat, refacing






a = 39.2 mm (1.543 in.)

b = max. permissible reworking dimension

C = approx. 2.0 mm (0.079 in.)

Z = cylinder head lower edge

30 ° = correction angle, upper

45 ° = valve seat angle

Exhaust valve seat, refacing






a = 32.4 mm (1.276 in.)

b = max. permissible reworking dimension

c = approx. 2.4 mm (0.094 in.)

Z = cylinder head lower edge

30 ° = upper correction angle

45 ° valve seat angle

CAUTION!

- Exhaust valve seat rings are provided with a neck. During reworking, make absolutely sure that the radius of the neck is not damaged