Exhaust Bolts or Studs?

[gwolc]

I am in the process of eliminating the heat exchangers on my 81 SC Targa. I have removed all of the old exhaust studs as some were damaged and another was broken. The Stainless Steel Headers have arrived and look great and I’m looking forward to installing them.

I have two questions concerning stud replacement:

A) Is there any thermal mechanical or other reason that favor using studs as opposed to bolts (either hex head or SHCS) to attach the headers?

B) Flanges on the heat exchangers were 9.7mm and had a 6.25mm spacer on top of the flange to compensate for the length of studs used (46.6mm LOA) – the flanges on the new headers are 8mm.

If studs are recommended, I would think the M8x30 (999-062-239-02-M58) would be a better choice than the 46.6mm studs that were installed.

Your opinions and comments are appreciated.

[James Brown]

No you need the long studs for the thick flanges. Bolts into soft aluminum is a recipe for disaster. the studs installed first reduces the chances of installation problems. and I don't think you can get bolts into the holes (clearance problems).

[Bob Kontak]

Additionally, for nut removal, you can put heat right on the nut and turn it cherry red in "no time". The bolts, assuming you could get them in, would require heating the head at the mounting flange rather than at the point of thread contact. Probably do-able, but way less hassle with the nut right there.

[gwolc]

Thanks for your input; I’ll get the studs ordered.