How do they sound?
 

I am looking at a 07 Heat with a Ilmor 710 how does this motor sound I like V8 rumble and I have not ever heard one run?

I ran in the Knoxville poker run 2 weeks ago with a friend (Quent Byerly) who has a 7-10 in a 24' Lavey Craft.
It sounds much better than the 525 or 625.
The 525 sounds like a UPS truck to me. The 625 has a little better hit to (obviously more cam)..........the 7-10 sounds awesome. They must have put some serious compression on this motor, as well as an even larger cam to get to 700HP. I think you'll like it.
BTW, His Lavey will run in the low 90s. It is a smaller, lighter boat than a Heat, with a radical step bottom.
Steve