Valve Seat: Service and Repair

Valve seats, refacing
Special tools and equipment
^ Depth gauge
^ Valve seat refacing tool

Note:
^ When repairing engines with leaking valves, it is not sufficient to replace or replace valve and valves. It is also necessary to check the valve guides for wear. This particularly important on high mileage engines.
^ The valve seats should only be reworked just enough to produce a perfect seating pattern. The maximum permissible reworking dimension must be calculated before reworking commences. If the reworking dimension is exceeded, the function of the hydraulic lifters can no longer be guaranteed and the cylinder head should be replaced.

The max. 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 between end of valve stem and upper edge of cylinder head.
- Calculate max. permissible reworking dimension from measured distance and minimum dimension.
Minimum dimension:
Outer intake valves: 34.0 mm
Center intake valve: 33.7 mm
Exhaust valve: 34.4 mm
Measured distance minus minimum dimension = max. permissible reworking dimension.





Example:
*\ The max. permissible reworking dimension is shown on illustrations for refacing valve seats as dimension "b."





Reworking intake valve seat
a = 26.2 mm diameter
b = Max. permissible reworking dimension*
c = 1 .5-1 .8 mm
Z = Cylinder head lower edge
= 45° valve seat angle
= 30° upper correction angle
= 60° lower correction angle

Reworking exhaust valve seat
a = 29.0 mm diameter
b = Max. permissible reworking dimension*
c = Approximately 1.8 mm
Z = Cylinder head lower edge
= 45° valve seat angle
= 30° upper correction angle
= 60° lower correction angle
*) Calculating max. permissible reworking dimension, Refer to Valve Seat, Service and Repair.