VHT engine paint. The trick is to let the block go thru a couple of heat cycles and then paint it. Trust me on this, I painted my block and after a few heat cycles, the paint started to just flake off.
SO, and I know the guys will say this, prep work is the key but you will get the same results by doing what I did. And yes, I brushed my paint on and it hasn't bubbled, blistered or chipped in over 2 yrs now.