Valve Seats, Reworking
Special tools and workshop equipment required
- Depth Gauge
- Valve Seat Refacing Tool
Perform the Following
When repairing engines with leaking valves, it is not sufficient to rework or replace valve seats and valves. It is particularly important to check 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 reworking dimension must be calculated before work is carried out. If the reworking dimension is exceeded, the function of the hydraulic lifters can no longer be guaranteed. Therefore the cylinder head should be replaced.
Calculate Maximum Reworking Dimension
-- Insert valve and press firmly against seat.
If the valve is to be replaced as part of a repair, use a new valve for the calculation.
-- Measure distance -a- between end of valve stem and upper edge of cylinder head.
-- Calculate maximum permissible reworking dimension from measured distance -a- and minimum dimension.
Minimum dimensions
Intake valve: 33.8 mm
Exhaust valve: 34.1 mm
Measured distance -a- minus minimum dimension
= Max. permissible reworking dimension
Example:
| Measured distance -a- | 35.1 | mm | ||||
| - | Minimum dimension | 34.1 | mm | |||
| = | maximum permissible rework dimension(1) | 1.0 | mm | |||
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Reworking Intake Valve Seat
| Dimension | Intake Valve Seat | |
|---|---|---|
| Diameter a | mm | 39.2 |
| b | mm | maximum permitted rework dimension |
| c | mm | 1.8 to 2.2 |
| Z | Cylinder Head Lower Edge | |
| 45° | Valve seat angle | |
| 30° | Upper correction angle | |
Reworking Exhaust Valve Seat
| Dimension | Exhaust Valve Seat | |
|---|---|---|
| Diameter a | mm | 32.4 |
| b | mm | maximum permitted rework dimension |
| c | mm | 2.2 to 2.6 |
| Z | Cylinder Head Lower Edge | |
| 45° | Valve seat angle | |
| 30° | Upper correction angle | |