Raceware Head Studs on Exhaust Side?

[alphie]

Ok, is this a dumb thought?

Last year I did a rebuild on my 3.0 to 3.2 short stroke. I replaced all the head studs with steel studs. I have since taken the engine apart to do further upgrades.

I noticed that on the exhaust side there was some leakage between the head and cylinder of some cylinders (not all). I never got the chance to do a re-torque on the heads before dismantelling.

Question, I am considering replacing the exhaust studs with Raceware. Thus I would have regular steel studs on top and raceware on the bottom. Does this seem like a goofy idea??? Why not replace all of them? Well I figure the top steel ones are new and installed and I can save about 1/2 cost by just doing the exhaust.

-Rob

[911pcars]

If the factory and Raceware studs are equivalent, why not use the factory ones on the lower row?

The Raceware studs are stronger, but ultimate tensile strength isn't necessarily the number one priority in this application. If the thermal expansion rates are the same and high temperature strength is adequate, the factory studs should be fine. There is an historical issue of corrosion exposure on the lower row - probably more with Dilavar - could be a potential variable between the factory and aftermarket studs.

Sherwood

[alphie]

I'm guessing the thermal expansion rates are not the same between the 993tt dilavar headstud used on the 993 turbo. But point taken, if raceware thermal expansion is the same as stock steel then no reason for raceware.

[rvanderpyl]

I thought that was the point of all of the aftermarket studs, that their thermal expansion was closer to that of the cylinders. Otherwise why use them?. No one breaks the factory steel studs, they pull out of the case.