Have a 1980 302 with 1966 289 heads that have the slotted pushrod holes with screw in rocker studs. On 2 opposite cylinders the rockers have gotten off center of the valve stem tip causing some tip wear and has enlarged the slotted hole in the head for the push rod. Have crane cast non-rail rockers with the elongated rocker stud hole for a higher lift cam (mine is 480 lift). I've heard guide plates should not be used on these heads but now I have to do something. Anyone using guide plates with these early heads. Or any other suggestions.
Figure I'm going to have to now Tim. Just unsure why they got off center like they did. The shop that did the heads told me I didn't need them also. Can guide plates be used in conjunction with these heads without having to enlarge the slots in the head (make them round). Really don't want to pull the heads.
First of all, why would the rockers have gotten off center? That could be caused by the screw-in rocker studs not being located correctly (EXACTLY in line with the head slot and valve stem) or the valves/rockers/slots were already worn allowing things to move around. You need to find the reason for your problem to know how to fix it. To use guide plates you will have to open up the slots to prevent binding the p-rod.
If the push rods have enlarged the slots at all you will need to drill them out round and install guide plates. The slots work the same as guide plates. Did you use hardened push rods? As with guide plated you need to use hardened push rods with the slot heads. You could use a oil soaked rag under the slot holes and grease on the drill bit to catch most of the metal shavings while drilling. That would let you drill the holes without removing the heads. Just make sure that you get all and I mean ALL of the metal shavings while doing the drilling. Good luck. Don
Only occured on 2 rockers. The studs look aligned correctly with the slot and valve. All valve guides were replaced. Shouldn't new guide plates line up with the slotted holes? Do appreciate everyones response.
As an afterthought, are you using stock cast rocker arms? I've seen where the pivot ball or the socket inside of the rocker arm can wear funny and make things get out of alignment.
Yes they will to a point but, trust me when I say that you should not install guide plates with slotted heads. It will cause problems in the end. Trust me!!!! Don
