Valve Seat: Service and Repair

Valve Seat Reworking

Special tools, testers and auxiliary items required

• Depth gauge

• Valve seat refacing tool

• When repairing engines with leaking valves, it is not sufficient to rework or replace valve seats and valves. It is particularly important to check valve guides for wear on engines with longer running times.

• Only reface valve seats enough until a perfect contact pattern is obtained. The maximum permissible reworking dimension must be calculated before work is carried out. If the reworking dimension is exceeded, the function of the hydraulic lifters can no longer be guaranteed and therefore the cylinder head should be replaced.

The maximum permissible reworking dimension is calculated as follows:

- Insert valve and press firmly against seat.

• 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 max. permissible reworking dimension from measured distance - a - and minimum dimension.

Minimum dimensions:

• Intake valve 43.4 mm

• Exhaust valve 43.2 mm

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

Example





Reworking Intake Valve Seat





a diameter 35.7 mm
b 1.6 mm
° 45 Valve seat angle

• The 30° relief milling of the valve seat is always necessary due to flow ratios in the intake canal.

Reworking Exhaust Valve Seat





a diameter 31.4 mm
b 2.7 mm
° 45 Valve seat angle