Uprated head studs

[Ben]

I'm looking at getting uprated head studs to use in the new engine I'm building. I know a few people on here are using them and just wondered if someone would mind explaining why the head is less likely to lift when using them, because I cant get my head around it.

Do they not expand as much as normal head bolts? Or are you able to have them tightened to a higher torque?

Cheers, Ben