How hot can aluminum heads get before they warp?

[Stang_ROTY]

I talked with him today and he said checked the head gaskets several times to make sure that they fit correctly and didn't block my coolant passages. I have a stock type March pulley coming tomarrow which will hopefully help me. It has to....I hope. The rep. from March said that the set of pulley's I have kill my cooling bby 20%! That's pretty significant, right? As far as getting a new engine builder, I really can't. Everyone around here is Chevy, Chevy, Chevy. He really is the most reputable builder and takes a lot of pride in his work. I have no other avenues to explore. The reason he keeps bringing up the water pump is b/c he thinks the impeller might not be turning the right way, making my pump a standard rotation pump. If it was a standard rotation and I'm driving it the wrong way how could the engine cool?