Valve Seat: Service and Repair

Valve seats, refacing

Note: If a good seating pattern cannot be obtained by grinding valve they must be reworked.

Special tools and repair equipment required
^ Depth gauge
^ Valve seat grinding tool

Notes:
^ When repairing engines with leaking valves, it is not sufficient to reface valve seats and replace valve. Valve guides must also be checked for wear. This is particularly important on high mileage engines.
^ Valve seats should only be reworked just enough to produce a perfect seating pattern.
^ Calculate the maximum permissible refacing dimension before refacing.
^ If refacing dimension is exceeded, function of hydraulic valve lifters can no longer be guaranteed and cylinder head should be replaced.

Calculating maximum permissible refacing dimension
^ Insert valve and press it firmly against valve seat.

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





^ Measure distance -a- between valve stem end (upper edge) and top surface of cylinder head using a depth gauge.





^ Calculate maximum permissible refacing dimension from measured distance and minimum dimension.





Note: If the maximum permissible refacing dimension is 0 mm or less than 0 mm, repeat measurement with new valve. If measured result is again 0 mm or less than 0 mm, replace cylinder head.








Refacing valve seats