IIRCThe highest WHP numbers not gotten by a sponsored dragracer has gotten out of an H series was 393hp, and 230tq. It was a turbo'd H22 in a Honda Prelude running ~14psi, with a 100 shot of the NO2. The estimated cost of his motor alone was $12,000.

So...Good luck with that.

You want 500HP? Go big: no replacement for displacement.