Hi Smitty:

I missed this thread when it first went up. Congrats on the good R&D!. For comparison one of our customers made 1000 HP @ 6000 RPM with a short deck 540 on JimKid's dyno in Detroit. He used an Rtech supercooler on Holley EFI intake with FAST injection. Saw 9.5-10 psi with the older big M3, sorry don't remember the pulley but it seemed big to me. I would say the Holley intake is better at this RPM but a comparison of the curves is called for. He used ported iron heads and a solid roller cam so I would expect your heads/cam/intake to have more midrange. Take care.

Tom

I have run a very similar setup for the last 4 years with a FAST fuel injection. Using a 548 standard deck Bowtie block, Canfiled 355 heads, Howards solid roller 259/[email protected] .675/.675, I use the Holley fuel injection intake as well and a rebuilt Procharger intercooler AW504. It made 1125 HP at 5800 and peak torque of 1120 at 4700. The motor runs a M-4 with a 4.00 inch pulley on the top, I generally run the 4.5 inch pulley for everyday use. It pulled over 1000 ft/lbs from 4000 all the way thru 5200. I now run a 588 with the AFR 357 heads, same camshaft, it makes more power than the old motor for sure, but haven't redynoed. I run a 1.26 gear from Max machine Worx and pull a 32 Bravo 1 prop. Never had the boat past 5400 but it was still pulling. This is from memory because I scanned the dyno sheets into my computer a couple of years ago. A jetski buddy decided to douse my boat with a spray of water as I opened my computer to tune the FAST. Needless to say that was a painful experience and he was gracious enought to buy the computer I am on now.

Just went past 100 hours on this combo, boat cruises nice at 60 mph, has ran 99 mph, broke quite a few drive parts ( no uppers though) and mid 70's without the blower, been overall happy with this. I have NOT had the valve covers off since being on the dyno in 2007 so there is something to say for t/d shaft rockers and having a hydraulic roller cam spece'd by Bob Madera. Going to be tearing it down this winter, isn't hurt but is just starting to get some blowby, Smitty

Here's a manifold to go back on it .....I doubt you'll make more power but sure is Purdy .......

smitty,i just noticed this thread,very nice numbers,i did a pair of 522 in engines for a buddy last winter,m4 prochargers,i told him to expect 950 hp,these things made 1175 at 6000 rpm,now i am seriously thinking of selling my blowers&buy a set of m4 or m5,s.these are going in a 42 fountain,i think it will run upwards of 115 mph,until the imco sc drives take a chit,which i think will be real soon.

Who made the plenum? That is the one thing I never modified on mine at all, never thought there was anything to be gained there BUT you never know??!! I dragged up my old manifold thread for you and a couple other guys that have asked lately too, Smitty

Wilson Manifolds .....they made em for a twinn Turbo setup I believe .....They have the Merc Plenums and Intakes and are saying the Plenums will flow plenty......and You have proven the intakes can produce big power with your mods ....m

This is a old thread from 2007, I am going rebuild my motor again this winter, it has been together and running for 4 years though!! These Centrifugals DO make alot of hp fairly easy, Smitty

How big did you bore your throttle body? Where did you get the throttle plates? Did you have the manifold extrude honed, or was it ported by hand?

Thanks, Joe

Smitty did all the Manifold work By hand ...I believe he milled the runner height ...He has access to the Throttle Body Mods and not sure but he might make the Throttle Plates ....I'm sure will will chime in ....m

http://www.offshoreonly.com/forums/g...pi-intake.html