Valve Guide: Service and Repair

CAUTION: This procedure is not recommended owing to the difficulty of establishing truth with the center of the valve seat. It should not be attempted unless comprehensive machine shop facilities are available. A replacement cylinder head should be considered as an alternative.

- To fit the guide correctly, the interference should not be sufficient to cause the use of excessive force.
- After fitting a valve guide, the valve seat must be recut.
- Check the clearance between the valve guide and stem this should be 0.025-0.10 mm (0.001-0.0O4 in).
- Replacement guides are available in three sizes and have identification grooves machined into the shank.

NOTE: Valve guides, when fitted during initial engine assembly, are to the following dimensions and may be fitted in mixed form.

Standard (no identification) 12.73-12.75 mm (0.501-O.502 in)
1st oversize (one groove) 12.78-12.8Omm(0.503-0.504in)
2nd oversize (two grooves) 12.85-12.88 mm (0.506-0.507 in)
3rd oversize (three grooves) 12.98-13.00mm (0.511-0.512in)

- When new guides are to be fitted, they should always be one size larger than the old guide.
- To fit the guide correctly, the interference should not be sufficient to cause the use of excessive force.
- After fitting a valve guide, the valve seat must be recut.

Standard and 1st oversize valve guides--may be replaced in the following manner:
- To heat up the head, immerse it in boiling water for 30 minutes.
- Using a piloted drift, drive the guide out of the head from the combustion chamber end.
- Coat the new valve guide with graphite grease and refit the circlip.
- Heat the cylinder head.

Valve Guides:

- Using a piloted drift, drive in the guide (1) from the top until the circlip is seated in the groove.

2nd oversize guides--must have the cylinder head bore reamed to the following dimension BEFORE replacement:

12.95 mm + 0.012 mm -0.005 mm (0.510 + 0.0005 in - 0.0002 in)

- Immerse the cylinder head in boiling water for 30 minutes.
- Coat the guide with graphite grease, and, using 18G 1432, drift in the guide from the camshaft side until the circlip is seated in the groove.