[PeteKz]

Mike has more experience with 911 engines than I do, but I have not yet seen upper broken studs on the dozens of 911 engines I've looked at with valve covers off. Thus I would want to know more about those that had broken upper studs. Were the lower studs broken too? I would expect so, and I suspect that continuing to run the engine for a long time with the broken lower studs thereby put more stress on the upper studs, leading to their failure. Was there also leakage at the head/cylinder surface? Corrosion of the studs also would have contributed to their failure.

I agree with Magyar. No need for expensive race studs for your engine. Remember, the upper steel studs in your engine are "used" too. If you already have a set, I would put them in the bottom row. Used nuts and washers are fine too. One caveat: If any of the studs have corrosion pitting, then don't reuse those. And to prevent future corrosion and possible cracking, paint them before installing.