996/997 Exhaust Studs
 

I can't seem to find any information on why 9x6/9x7s use crap exhaust screws instead of studs with nuts. Seems like another case of aluminum not being the best material to screw things into repeatedly but I don't see anyone offering studs. Is it because exhaust components are expected to deteriorate and a screw is easier to replace than a stud? The crap screw twists off before you can damage the aluminum through over torqueing? Is it the chemistry between a stainless stud and the aluminum? Now I am curious and someone here knows!

Even cylinder head quality aluminum isn't great for repeated screwing (quip here) because the threads can become work-hardened (brittle) and/or gall.
Porsche may have chosen stainless screws since they tend to have a smoother thread finish and don't oxidize (like steel bolts/screws).

Are you removing the exhausting manifolds often?

If space allowed, or the next time you remove the engine, you could install Heli-Coils or Perma-Coils in the heads.

Switching to studs also makes sense. Take your screw size and check ARP's website for studs/nuts with those pitch/thread dimensions and about 10 mm longer length.

On the chemistry side, stainless (active) and aluminum are relatively close on the Galvanic Series and anodic, so it's less likely you have a galvanic interaction occurring. If the cylinder head stainless is passive, that could be an issue. Does anyone know the material specs for the cylinder heads?
If you added water, better yet saltwater, galvanic action would be a bigger issue. Here's one of the zillion charts on the web

I've drilled out many exhaust bolts on the early 996's and they are not stainless. They are soft mild steel. And I haven't encountered any helicoils either. I am of the opinion that porsche just wanted to save money and used bolts rather than stud and nuts. I would recommend either never seize and/or helicoil.

Just to clarify, I said the OE screws were made if CrAp but assumed any studs would be stainless. Currently I am using ceramic anti seize and have been removing the headers more than anticipated. :bang: I had two screws fall out at the last DE at OE torque spec which set me to thinking. So far no problems with broken screws but everyone I know has had to drill a few out.