Which Rb Engine Combo?

[fletch rb30]

I have a 25/30 with gt35/40 turbo. 1.06 rear housing. stock rb20/25det exh manifold. it makes 260rwkw with pretty much stock everything.

the guy i bought the turbo off had a single cam rb30 with forged rods and pistons. he was making 550hp at the fly with 27 or 29psi boost and stock inlet manifold and cam etc. he got head ported, big cam, big valves etc ($$$) and made 652hp on 20-22psi but the engine was really working hard and he had ongoing problems.

i put a stock rb25vvt head on a stock rb30 bottom end and its making 400hp at the fly, a bit more tuning and it will easily make 500hp. all up cost was around $6-7k. just used standard rebuild parts, rings bearing gaskets etc, and got he front oil gallery welded up and did the vvt feed line off the oil pressure sender with a tee fitting.

[The Ant]

You seem to only want people to confirm for you to use the rb30 head. Do what you want, but at the end of the day, the rb25 head will be better, which is what everyone else is telling you.

I'm just trying to get to the nitty gritty and be explained technically why not use the rb30 head and how much difference are we talking about here. Is it marginal or is it like 40% or more in difference?

Edited May 11, 2008 by The Ant