Reuilding two engines 515cu/in 4.5 bore tall decks 4.25 stroke 8.25 dish pistons 671 blowers with coolers. The heads that where on it where Merlin 320 runners with 2.15/1.88 valves. Heads cracked so I am shopping for a replacment set. An OSO member has a set of Dart Iron Eagle Heads: 15100010 Intk runner: 308cc /Cham.: 119cc / Int/Exh: 2.25/1.88. Are the runners too small?

With 4 or 5 psi the IE's probably wouldn't be too bad. With chillers and bigger boost, my guess is you'd be giving up 100 to 150 hp minimum. Maybe more.

Are your present heads beyond repair? I've seen miracles performed on aluminum heads.

If you are considering going aluminum, PM me. I have a deal in the works on heads.

I personally think 308's are way too small for a 500+ci motor with a blower. I'd personally go with like some 335's or 340's.

Nasty frozen heads, crummy pix

This is something I've been looking into extensively for the last month. I've spoken to just about everyone who will talk about it and I keep coming up with the same answer- For a pump-gas 500/540, there's probably no better head than the AFR 315CNC.

This is what I've learned- it has an almost ideal port flow to velocity relationship on the intake and a high intake/exhaust ratio which is more critical on a blower motor. The downside is expense. I'm working on that one right now- I've spoken to a manufacturer who's working on something for me right now. I'll post the info when I know more.

Freezing

There are limits to what you can weld.

Just as an aside, 4.5" bore/4.25 stroke is 540 cubic inches, not 515. You'll want even more flow....

Wow! Rarely is it bigger than a guy estimates.

My screw up 4.54 bore/ 4.0 stroke(just measured it) =518cu/in

Andy,

Are those iron heads? I assumed aluminum when I read Merlin- incorrectly?