SharkSkin

In a race car application that's probably fine. That's not something that you expect to stay bolted together forever anyway. Very likely you will be pulling those header bolts out before the threadlocker deteriorates enough to matter. In fact, even broken-down threadlocker clogs the threads enough to help somewhat in preventing bolts from vibrating free.

After seeing your post, I trudged out to the garage and looked at the tube... 271 threadlocker. Right. Always, when I see that number I wonder how I could forget it, but I do. I just ask for Loctite "Red".

So I proceeded to do a little research, and it turns out that my recollection was off; the breakdown temp(what they are now calling "Disassembly Temp") is 232°C, which works out to about 450°F.

For your application, you might be interested to know that the threadlocker will lose half its strength in 500 hours at 150°C or 300°F, about 2/3 of its strength in 1000 hours, etc. You might also be interested to know that it is only rated for applications to 150°C.

More details here. (no affiliation )