Valve seats, reworking
WARNING: This page is about a different variant/trim than selected.
Special tools, testers and auxiliary items required
- Depth gauge
- Valve seat refacing tool
NOTE:
- When repairing engines with leaking valves, it is not always sufficient to merely reface or replace valve seats and valves. It is also necessary to check the valve guides for wear. This is particularly important on high mileage engines.
- The valve seats should only be reworked enough to produce a perfect seating pattern. The maximum permissible reworking dimension must be calculated before reworking starts. If this dimension is exceeded, the hydraulic lifter function can no longer be guaranteed and the cylinder head should be replaced.
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 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 35.8 mm; Exhaust valve 36.1 mm
Measured distance minus minimum dimension = maximum permissible reworking dimension.
Example:
| Measured distance | 36.5 mm |
| - Minimum dimension | 35.8 mm |
| = Maximum perm. rework dimension | 0.7 mm |
Reworking intake valve seat
| a | = | 35.7 mm diameter |
| b | = | 1.6 mm |
| 45 ° | = | Valve seat angle |
NOTE:
- The 30 ° lower valve seat chamfer is necessary to ensure that the intake channel flow characteristics are maintained.
Reworking exhaust valve seat
| a | = | 31.4 mm diameter |
| b | = | 2.7 mm |
| 45 ° | = | Valve seat angle |