924Board.org

[dvarholy]

I have had several of the 8x25mm exhaust manifold studs break over the years on different 931's I have worked on. In the Porsche parts manual, it mentions that the 90008105300 studs have been replaced with n90073001 "of a different material." I have also heard suggestions to use stainless steel studs. What holds up the best over time? We all know just how hard these things are to replace (and how expensive those 930 gaskets are). Usually, its the #3 or #4 cylinder on the top that breaks off after about 30,000 miles or so.

[larso]

I'm not sure if this is a solution but I find that if you put the exhaust studs too tight it may cause the expansion of the manifold to be restricted, and then cause this restricted force to become a crack in the manifold, or a break in the stud. I'd say the best material of stud would be of the same material type that the manifold is, so that both metals expand the same. Maybe using the locking nuts and not putting the manifold on really really tight would help, I haven't had enough experience but I am guessing that maybe they are overtorqued. The nuts always come loose of you don't have the locking ones, so it's important to get those 12 dollar a piece locking ones form the dealer! I want to get some locking nuts for cheaper from a nut and bolt warehouse, but I am unsure of what material the nuts are made of. Are they stainless? The little bit of gold color to them makes them look special, but paying 12 bucks for a nut is ridiculous.