Valve Seat: Service and Repair

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

Work sequence

Note:
^ When repairing engines with leaking valves, it is not sufficient to rework or replace valve 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, Testing and Inspection
^ 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.

- Remove camshafts, Refer to Camshaft, Engine, Service and Repair

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 measuring.





- 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
Measured distance minus minimum dimension = Max. permissible reworking dimension.





Example:
*) The max. permissible reworking dimension is shown as dimension "b" in illustrations for the reworking of valve seats.





Reworking intake valve seat
a = Diameter 30.6 mm
b = Max. permissible reworking dimension*
c = 0.91.5 mm
d = Max. diameter 35.0 mm
r2 = Radius 2.0 mm
z = Lower edge of cylinder head
En = 45° valve seat angle
*= 30° upper correction angle
f2 = 60° lower correction angle





Reworking exhaust valve seat
a = Diameter 26.7 mm
b = Max. permissible reworking dimension*
c = 1.21.7 mm
d = Max. diameter 29.0 mm
r2 = Radius 2.0 mm
z = Lower edge of cylinder head
En = 45°valve seat angle
B= 30°upper correction angle
-I' = 60°lower correction angle