Valve Seat: Service and Repair

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

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

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 between end of valve stem and upper edge of cylinder head.
- Calculate maximum 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 = maximum permissible reworking dimension.








Example:

The max. permissible reworking dimension is shown on illustrations for reworking valve seats as dimension "b".





Reworking intake valve seat

a = 26.2 mm diameter
b = Max. permissible reworking dimension*
c = 1.5 to 1.8 mm
Z = Cylinder head lower edge,
a = 45° valve seat angle
p = 30° upper correction angle
Y = 60° lower correction angle

Reworking exhaust valve seat
a = 29.0 mm diameter
b = Max. permissible reworking dimension*
c = Approx. 1.8 mm
z = Cylinder head lower edge
c = 45° valve seat angle
p = 30° upper correction angle
Y = 60° lower correction angle
*) Calculating max. permissible reworking dimension.