The valve guides should be cleaned and checked when valve stem diameter and stem-to-guide clearance is checked. Generally, if the engine is using oil through the guides (assuming the valve seals are OK) and the valve stem diameter is within specification, the guides are worn and need to be replaced.
Valve guides which are not excessively worn or distorted may, in some cases, be knurled rather than replaced. Knurling is a process in which metal inside the valve guide bore is displaced and raised (forming a very fine cross-hatch pattern), thereby reducing clearance. Knurling also provides for excellent oil control. The possibility of knurling rather than replacing the guides should be discussed with a machinist.
REMOVAL & INSTALLATION
See Figures 1 through 5
- With the cylinder head removed from the engine, and the valves removed from the head, use a drift and a hammer or press. Drive the valve guides out from the combustion chamber side toward the rocker cover side. A heated cylinder head will facilitate this operation.
- Ream the cylinder head-side guide hole at room temperature. The guide hole should be: