A good exhaust flange sealer?

[Bonnewagon]

think I just threw two of those out.

 

[64nailhead]

I use the permatex ultra copper.

Me too. I have sealed header flanges on turbo builds with nothing other than Permatex Ultra Copper. How this stuff seals 1800-2000 degrees of heat at 40-50psi of pressure is beyond me, but it works.

 

[bs009]

If you can weld a new flange on there I've had a lot of success with stainless steel v-band flanges on exhaust components. Would not use regular steel only stainless steel.
One nut to remove, no gasket or rtv needed, but you do need to put some effort into aligning the pipes really well when you tighten the v-band itself.
I can't see myself ever going back to a bolt on flange now

 

[olds307 and 403]

Permatex Optimum Grey. Good to 700F, very heavy body and looked like new after a year when I removed my headers. It is much more rigid and less noticeable than Ultra Copper.