The valve guide is a bronze cylinder the valves run up and down in.
Another fix for the drilled thru hole depending on how much material is there would be to put a set screw in the bottom. Measure the length of the hole, You need enough length so the valve cover screw won't bottom against the set screw. The set screw should still have 1/4-5/16 of it's thread in the material. Then use some thread sealer on the set screw and run it down. This is essentially what you are going to have to do with the head bolts as they also go into the water jacket.
Larry
Last edited by LGriffin; 04/24/2010 4:07 PM.
