Valve Seat: Service and Repair

Valve seats, reworking

Special tools, testers, measuring instruments and auxiliary items required

^ Depth gauge
^ Valve seat refacing tool

Note:
^ When repairing engines with leaking valves, it is not sufficient to reface the valve seats and replace the valves. The valve guides must also be checked for wear. This is particularly important on high mileage engines.
^ Only rework the valve seats as far as is necessary to ensure a good seating pattern.
^ Before starting to rework the valve seats, calculate the maximum permissible reworking dimension.
^ If the maximum reworking dimension is exceeded, the hydraulic lifters will not work properly and the cylinder head will have to be replaced.

Calculating maximum permissible reworking dimension

- Insert valve and press firmly against valve seat.

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

- Measure distance between end of valve stem and central axis of camshaft (central axis of camshaft is level with top of cylinder head.)
- Calculate max. permissible reworking dimension from measured distance and minimum dimension.





Measured distance minus minimum dimension = max. permissible reworking dimension.





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





Reworking valve seats