Valve Seat: Service and Repair

Valve seats, finishing

Necessary special tools, operating equipment, testers, gauges and other aids:
- Depth gauge
- Valve seat finishing tool

Procedure

Notes:
- When repairing engines with leaking valves it is not sufficient to just work on or replace valve seats and valves. With longtime engines in particular it is necessary to check valve guides for wear.
- Only finish valve seats until a correct contact pattern is achieved. Before finishing valve seats you need to calculate the allowable finishing measurement. If this measurement is exceeded, correct functioning of the hydraulic valve clearance balancing cannot be guaranteed and you must replace the cylinder head.

Calculating the maximum allowable finishing measurement
- Insert valve and press firmly against valve seat.

Note: If the valve is being replaced during repairs, use a new valve for measuring.





- Measure distance -a- between valve stem end and upper edge of cylinder head.
- Calculate maximum allowable finishing measurement from measured distance and minimum measurement.
Minimum measurements:
- Intake valve: 33.9 mm
- Exhaust valve: 34.1 mm
Measured distance -a- minus minimum measurement = max. allowable finishing measurement.





Example:
Measured distance -a- 34.8 mm
- minimum measurement 34.1 mm
= max. allow. finish. measurement 1) 0.7 mm





Finishing intake valve seat
a = dia. 38.3 mm
b = max. allowable finishing measurement
c = 1.4 - 2.0 mm
If necessary, finish valve seat ring with 75° valve reseating tool
Z = bottom edge of cylinder head
cr = 45° valve seat angle
P = 30° correction angle upper
-= 60° correction angle lower





Finishing exhaust valve seat





a = dia. 33.5 mm
b = max. allowable finishing measurement
c = 2.0 mm - 2.5 mm
If necessary, finish valve seat ring with 75° valve reseating tool
Z = bottom edge of cylinder head
1:= 45° valve seat angle
p = 30° correction angle upper
- = 73° correction angle lower