I’ve got the remflex in last night but they are so thick, I’m afraid the nuts wont engage the threads enough. Do they squish a lot?
They do squish a bit but not a lot. Look at the pic I posted to AndyF's thread on the Milodon Sandwich Plate ... you can see the Remflex Gaskets torqued down and how much they squish (not much). I'm using Percy's locking header bolts that are 3/4" long (
https://www.summitracing.com/parts/php-310014/overview/) and there is plenty of thread engagement. And I've had these headers on and off while reusing the gasket and never had a leak. I HATE header leaks ... they drive me nuts!! My heads are aluminum but the gaskets didn't stick when I removed/reinstalled the headers. My experience is that as long as you put them back on with the same headers and in the same orientation, they can be reused. They have a sort of non-stick graphite coating on them. If you are running iron heads with studs, you might have to put in studs that are just a bit longer. Not sure if they might stick to cast iron after a bunch of heat cycles.