Valve Seat: Service and Repair

Valve Seat, Refacing

Special tools, testers and auxiliary items required

• Depth Gauge

• Valve Seat Refacing Tool

• When repairing engines with leaking valves, it is not sufficient to reface or replace valve seats and valves. It is particularly important to check the 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 refacing dimension must be calculated before the work is carried out. If the refacing 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 Refacing Dimension is Calculated as Follows:

- Insert the valve and press it firmly against the seat.

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

- Measure the distance - a - between the end of the valve stem and the upper edge of the cylinder head.






- Calculate the Max. permissible refacing dimension from the 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 refacing dimension.

Example:






Refacing the Intake Valve Seat






a 35.7 mm diameter
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.

Refacing the Exhaust Valve Seat






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