That's a tuff question, and i don't know what the right answer would be, as suggested 1,000 to 1,100 max.
What i do know is when i was running a 540" 1471 on alcohol. i mistakenly tacked the outher slip tubes to the inner tubes/ headers and after the pass the outer slip tubes wrinkeled up so much they looked like a corrigated hose, i never did that again. I'm thinking i was probable in the 1500/1600 degree range for them to do that (i didn't have an EGT setup), but that's where it ran best at 8,000 RPM's. That was a Rodex blk with Brodix solid heads, but 25 yrs ago.
zip.