Valve Seat: Service and Repair

Valve seats, refacing
Special tools and equipment:
^ Depth gauge
^ Valve lapping tool

Note:
^ Repairing engines with leaking valves, especially engines with high mileage must include measuring valve guides.
^ Before refacing, calculate maximum permissible refacing dimension.
^ If the maximum permissible refacing dimension is exceeded, the function of the hydraulic valve lifters can no longer be guaranteed and the cylinder head must be replaced.
^ Reface valve seats just enough to produce a good seating pattern.

Maximum permissible refacing dimension, calculating
^ Install valve and press it firmly onto the valve seat.

Note: If valve is to be replaced, use new valve for measurement.

^ Install valve and press firmly against valve seat.
^ Measure distance between end of valve stem and top surface of cylinder head.
^ Calculate maximum permissible refacing dimension from measured distance and minimum dimension.

Minimum dimensions





The measured distance minus the minimum dimension equals the maximum permissible refacing dimension.

Example:
Outer intake valve
Measured distance 34.4 mm (1.354 inch)
Minimum dimension - 34.0 mm (1.338 inch)
Maximum permissible refacing = 0.4 mm (0.0157 inch)

Note: If the measured distance is less than the minimum dimension, repeat the measurement with new valves or replace the cylinder head.





^ Valve seats, refacing