[Scott Liggett]

Are you running 1.5 or 1.6 ratio rocker arms. For 1.6 ratio rockers, I would recommend 7/16" studs. Easy enough to change.

Many aftermarket heads with 195cc or bigger intake ports will cause the intake side of the rocker arm to be slightly cockeyed. This is very common. Several head companies have this notice on their website. This picture shows the intake way off. But, often times when one rocker, valve spring, or pushrod fails on a cylinder, the other gets knocked out of whack from the back pressure or firing of a valve suddenly slamming shut.

Guide plates are supposed to be softer than the pushrods. They are the sacrificial lambs when pushrods rub too hard against them. That is why you are supposed to run hardened pushrods with cylinder heads that have guide plates.

In any case, this could be nothing more than a parts failure from anything from bad metallurgy to something going wrong in the machining process of the stud. Unless you start having several failing, one after the other, then I wouldn't worry too much. Worst case, you call up someone like Comp Cams and replace all the rocker studs and guide plates.

When you replace everything, reset the valve lash and roll the engine over making sure the rocker is not binding or hitting the stud or valve spring. Also make sure the rocker is staying center over the valve tip.

Good luck.