Note. When servicing engines with leaking valves, refacing or replacing valve seats and valves is not sufficient. It is particularly important to check valve guides for wear on engines with higher running performance. See VALVE GUIDES, CHECKING . Only reface valve seats enough until a perfect contact pattern is obtained. Before refacing, determine maximum refacing dimension. If refaced dimension is exceeded, hydraulic valve lifter function is no longer guaranteed and cylinder head must be replaced.
Scheme 321
- Insert valve and press tightly against valve seat. NOTE: If valve is replaced during repair, use new valve for measurement.
- Measure distance -a- between valve stem end (upper edge) and upper cylinder head surface using a depth gauge.
- Determine maximum allowable refacing dimension using distance measured and minimum dimension.
| Minimum dimensions | ||
|---|---|---|
| Outer intake valves | Center intake valve | Exhaust valves |
| 31.0 mm | 32.2 mm | 31.9 mm |
DISTANCE BETWEEN VALVE STEM END (UPPER EDGE) AND UPPER CYLINDER HEAD SURFACE
Measured distance minus minimum dimension = max. permissible refaced dimension.
| Example for outer intake valve | ||
|---|---|---|
| Distance measured | 31.4 mm | |
| Minus | Minimum dimension | 31.0 mm |
| Equals | Maximum allowable refaced dimension | = 0.4 mm |
MAX. PERMISSIBLE REFACED DIMENSION SAMPLE CALCULATION
Note. If the maximum allowed refaced dimension is 0 mm or less than 0 mm, repeat measurement using new valve. If measurement result is still 0 mm or less than 0 mm, replace cylinder head.
