How hot can aluminum heads get before they warp?

[Stang_ROTY]

I'm trying to see if the water pump is the problem so after I replaced the crank pulley with the standard diameter and start the engine with the rad. cap off. I let it run a few minutes and then it starts to blow the coolant out onto the ground. Does this mean that I have the wrong water pump. It's supposed to be a reverrse rotation Edelbrock. But if it's blowing out does that mean it's a standard rotation?? I'm going to post a new topic for this one.