Valve Guide: Service and Repair

REAMING





If the valve stem-to-valve guide clearance exceeds the service clearance, ream the valve guide for the next oversize valve stem. Valves with oversize stem diameters of 0.38 mm and 0.76 mm (0.015 inch and 0.030 inch) are available in diameters of 0.41 mm and 0.81 mm (0.016 inch and 0.032 inch) oversize.

NOTE: If it becomes necessary to ream a valve guide to install a valve with an oversize stem, a hand-reaming kit is available which contains the following reamer and pilot combinations:
A 0.38 mm (0.015 inch) OS reamer with a 0.76 mm (0.030 inch) OS pilot.
A 0.76 mm (0.030 inch) OS reamer with a 0.38 mm (0.015 inch) OS pilot.

1. Hand ream the valve guide.
2. When replacing a standard size valve with an oversize valve, always use the reamer in sequence (smallest oversize first, and then next smallest and so forth) so reamers will not be overloaded.
3. Always reface the valve seat after the valve guide has been reamed.
4. Use a suitable scraper to break the sharp corner (ID) at the top of the valve guide. Failure to do so may result in possible valve train wear and/or damage.
5. Reface valve seat as required. Install standard-size valve stem seal.
6. Check valve lash (collapsed tappet gap).

REPLACEMENT
If oversize valve stems and oversize valve stem seal are not available:
1. Press out original guide and install service bushing.
2. Ream ID for specified clearance for standard-size valve.
3. Reface valve seat as required. Install standard-size valve stem seal.
4. Check valve lash (collapsed tappet gap).