REMOVAL & INSTALLATION
See Figure 1
Worn valve guides can, in most cases, be reamed to accept a valve with an oversized stem. Valve guides that are not excessively worn or distorted may, in some cases, be knurled rather than reamed. However, if the valve stem is worn reaming for an oversized valve stem is the answer since a new valve would be required. Knurling is a process in which metal is displaced and raised, thereby reducing clearance. Knurling also produces excellent oil control. The possibility of knurling instead of reaming the valve guides should be discussed with a machinist.
Diesel engine valve guide bores have a wear limit of 0.3815 in. (9.7mm). If the valve guide bores are larger than the wear limit, the cylinder head must be machined for service valve guides. Consult a machinist.