ghittner

Just finished my motor, a 454 stretched to 496, with a B&M 420 Megablower, dual 750's on top and all the good stuff inside. I'm running the World Pro Merlin steel ovals because that's what I have and I've spent too much already. Would the rectangulars make more power at 12pds of boost or under? If so, how much? No dyno, I'm guessing approx 800-850 HP w/no intercooler. Am I close here?

jspeeddemon

I would say you are close on the hp number at that boost level and I would think better flowing heads make a differnce, but at what price. The biggest downfall to Merlins, I believe they lack the advantage of raised exhaust ports, which hurt there flow, and hurts power on a supercharged application.

ghittner

Thanks for the info. I'm pretty sure the exhaust ports are raised about 1/2 inch over the GM heads.

ratman

you will need i big exhaust system too

ghittner

Got it, Stainless Marine 4" wet pipes no mufflers.

articfriends

iTrader: (1)

Not trying to be confrontational here but the exhaust flow numbers on merlin heads are barely over 200 cfm un-ported. The intake ports flow around 280 cfm,your forced induction will force them to flow make them flow more but the exhaust still acts like a normally aspirated engine. I was running merlins rectangle ports on my blown 540 and when I went from 8.5-9 psi boost to 12 psi it gained virtually nothing,I blame it on the restrictive exhaust. I think you'll be closer to 700hp and 800 ft lbs of tq and at that point until you either port exhaust side of heads a extreme amount or jump up to some heads with much better flowing exhaust ports it will be hard to see signifigant gains. I switched to afr cnc 315's that flow 375intake/310 exhaust compared to your 283 intake/214 exhaust (pretty much 30% more) and made over 900 hp at 10 psi of boost in comparison (but with 40 more cubic inches),exhaust flow is important on a blower motor and your heads WILL hold you back. Maybe I'm off base but thats what Ive seen,Smitty

ghittner

The more input the better