Valve Seats, Refacing

Valve Seats, Refacing


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

Note:
When repairing engines with leaking valves, it is not always sufficient to replace or replace valve seats and valves. It is also necessary to check the valve guides for wear This particularly important on high-mileage engines.

Calculating max. permissible refacing dimension

- Insert valve and press firmly against seat.

Note:
If the valve is to be replaced as part of a repair use a new valve for the measurement and calculation.





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

The measured distance minus the specified minimum dimension is the maximum permissible refacing dimension,the maximum amount of material that can be removed when refacing the valve seats.

Minimum cylinder head dimensions

^ For intake valves 33.8 mm (1.331 in.)

^ For exhaust valves 34.1 mm (1.343 in.)




Example:

Note:
^ If the measured distance -a- is smaller than the specified minimum dimension, measure again using new valves.
^ If necessary use shorter valves (valve length - Fig. 4) or replace the cylinder head.

Intake valve seat refacing dimensions





a - 39.2 mm (1.543 in.)

b - maximum permissible refacing dimension

C - approx. 2.0 mm (0.079 in.)

Z - cylinder head lower edge

45° = valve seat angle

30° = valve seat upper correction angle

Exhaust valve seat refacing dimensions





a - 32.4 mm (1.276 in.)

b - maximum permissible refacing dimension

c - approx. 2.4 mm (0.094 in.)

45° = valve seat angle

30° = valve seat upper correction 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.

Fig. 4 Valve dimensions








Caution!
DO NOT recondition valves by cutting or grinding; only hand lapping is permitted.