UPDATE - Yes

So I'm trying to get a better seal on for my headers to heads. I can't weld, yet. So I found a SS welder nearby. Looking at the exhaust tubes through the heat exchanger hole I see surface rust. Are the tubes themselves also SS or just the casing for the heat exchangers? Can I just use regular mild steel welding?

Yes they are stainless.. Stainless rusts as well and depending on alloy will lead into how quickly they rust. 400 series rusts quicker then 300 series and different uses. Those were likely 304 ss

Thanks for the quick answer.

400 series SS is magnetic and 300 series SS is non-magnetic.

400 stuff (12% Chrome ,balance mostly iron) is what SS knives are made from and can be heat treated to obtain hardness, rusts easily

300 stuff (18% Chrome, 12% nickel, balance mostly iron) does not respond to heat treatment for hardness, much more rust resistant

Note that there about a dozen grades of each with slightly varying minor elements

Be careful.

Take careful measurements of the centers for the mounting tabs and the tubes on these.

I used an old head when my tabs broke off like this. Even then a had to do some manual stress reliving. (Dead blow hammer).

The tubes WILL move when you weld them. That is why the welds break....they were lousy to begin with. Weld the tabs on BOTH sides using TIG.


BTDT

Yup I know but didn't want to over complicate the thread.. Below is a sample of my 304 ss heat exchangers.Click to view attachment

Some early SSI's had mild steel muffler flanges, the rest was SS.