REMOVAL & INSTALLATION
Replacing the valve guides involves heating the head to high temperatures and driving the old guide out with the use of special tools. The head may have to be machined for an oversize guide if the bushing bore dimension is over the standard specifications. The new guide is then reamed for the proper valve stem-to-guide clearance. This repair requires a high level of mechanical skill and should only be performed by a reputable machine shop.
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, thereby reducing clearance. The possibility of knurling rather than replacing the guides should be discussed with a machinist.