Valve Seat: Service and Repair

Valve seats, reworking

Special tools, testers and auxiliary items required
^ Depth gauge
^ Valve seat refacing tool

Note:
^ When repairing engines with leaking valves, it is not sufficient to rework or replace valve seats and valves. It is also necessary to check the valve guides for wear, particularly on high mileage engines.
^ Valve seats should be reworked only enough to produce a perfect seating pattern. Before beginning to rework valve seats, calculate the maximum permissible reworking dimensions. If the reworking dimension is exceeded, hydraulic valve compensation can no longer be guaranteed and the cylinder head should be replaced.

The maximum permissible reworking dimension is calculated as follows:
- 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 calculation.





- Measure distance - a - between end of valve stem and upper edge of cylinder head.
- Calculate maximum permissible reworking dimension from measured distance - a - and minimum dimension.

Minimum dimension:
- Intake valve 33.8 mm
- Exhaust valve 34.1 mm

Measured distance - a - minus minimum dimension = maximum permissible reworking dimension.
^ The maximum permissible reworking dimension is shown on illustrations for reworking valve seats as dimension "b".








Reworking intake valve seat








Reworking exhaust valve seat





Note
^ Exhaust valve seats are additionally fitted with a restriction. When reworking, always ensure that the radius of the restriction is not damaged.