They also have wet sleeves in them and have water flow around them. That's how the 4 cylinder blocks were done. Kinda' like how a diesel is. Removable liners that interlock in the deck. But most billet blocks I've seen are solid and intended for short duration racing and for use with Methanol or Nitro as a fuel.
The IGOR block and other components were a true one off, and there really wasn't any other way to make them for it's intended purpose.
That makes a cast block more advantageous because, while many things can be made billet, I do it professionally for a living everyday, many things just aren't practical to be made that way.
