454 build opinions
 

I just picked up a 26 ft single engine boat project that I'm bravo swapping and building a 454 for it using parts I have in stock for it. starting with a 4 bolt 454 block that's 30 over, stock gm forges crank, eagle h-beams, weisco forged dome pistons, dart 308 iron heads, 500 efi or 525 efi cam, gil exhaust, gonna try to keep compression at 9.2-9.5. I have 3 intakes to choose from, a Holley strip dominator, a professional products single plane, and a Weiand stealth dual plane. which intake would be best suited. hoping for around 500 hp if possible, I will be using a 525sc ignition and starting with a holley 750 I have until I can find a 800cfm marine carb. any advice is appreciated.

sell all those intakes and buy a performer rpm, the "style" of the weiand stealth intake is best choice of the 3 BUT has TERRIBLE distribution issues and you couldnt pay me to run one on a boat. I had a customer build a mild 502, stock heads, weiand stealth. On my dyno with 10 02 sensors # 3 was 15+ to 1 afr, 2 was in the tens, a 5+ point spread. 2 was coal black and 3 had zero color, pure white. Theres no carb spacer or stagger jetting that can fix that since those 2 ports are fed by same bbl. There was another pair almost as bad. IF you look, the port feeding 2 is 1.5 times bigger then 3 and funnels all the fuel to 2 and starves 3 as fuel cant turn the sharp corner. Puzzled by this I dragged a stock merc dual plane out pff a early carbed 502, it had the same exact ports as if the weiand was a copy of it EXCEPT the mercruiser/gm intake had grooves in floor casted in to turn the fuel, the weiand did not. All intakes suffer from distribution issues in various ways, the weiand was exceptionally bad to where it would have turned 3 to ashtray at wot unless you jetted that corner so fat it drove 2 into the 9-1 afrs. We switched to a performer rpm, it made more overall power and afr spread from leanest to rich was onnly about 2.5 points which is typical, Smitty

The RPM air gap is the way to go

you guys did read he has a 26 foot boat,right.

yes and a performer rpm which is a dual plane works great at making torque right off idle and beats a open plenum in every possible way until about 5400 to 5600.

Love my performer RPM, dual plane is the way to go on a boat

on different Engine Masters shows with all brands of street engines they tries multiple intakes and time and again the best overall intake was the Performer RPM. they even commented that no matter the street engine the RPM always won out.

Exactly, a small motor in a 26 ft boat, he needs all the torque he can get.

the boat in question is a 26 phantom which looks like a copy of a 26 martini. It runs low 60s with a 454 mag and a trs that's in the basement. Hoping a bravo swap and 475-500 hp get it into the low 70s

26ft hull with molded swim step? Or 26ft from transom?
Whay does the hull weigh ready to fun with fuel?
What is Is your speed goal?

If you have all 3 intakes...put the DP on, and see how it performs. Part throttle cruise + WOT.

If you have room in the bottom end, try out the SP. See if you gain any MPH.