Allan4

Hey guys, I have a question for you. I built a 509 last year, 520hp/575Ft-lbs-tq. Blueprinted, balanced, everything new or reconditioned. Hydro roller, about 9.5:1 to 9.9:1 cr, probably closer to 9.9. I bought a Weiand 177. Am I safe at 5 psi? Will my 850 holley double pumper be big enough with jetting. I am currently running 80's on all corners. How much power should I expect out of 3 psi and 5 psi. I am guessing about 60 hp @ 3 psi and maybe 90ish hp @5psi. Is that close??

Thanks for your help!!

jdnca1

What are your cam specs? never mind I see them.

cigarette1

That blower is too small for a 509.

Gary Anderson

I would guess that you would get nearly 700hp at 5psi and a 9.9:1 CR. You would have to run VERY high octane though (over 100). And that blower is small for a 509.
I personally think it's a bad idea unless you lower the CR to 8.5 or under. And a larger blower wouldn't hurt either.
My $0.02
Gary

Cignificant

Gary, you think a 177 on that engine will provide and additional 180HP? I've never dyno'd any of my blower motors, but I've been told that a 502 with 8.75CR with a twin carb 250 is only good for about 650HP. Single carb you're looking at 625HP.

No matter what, I think a 177 is too small for that engine. There were 174s on my 502s when I bought my boat and they had to work their butts off...

Gary Anderson

Cignificant
I'm just guessing based on my results with a 454 and a 177 blower. Either way, I agree, you're going to have to really spin that little blower to get 5 psi.
And I wouldn't doubt you could get nearly 700hp with that 9.9:1 CR. At least until detonation destroyed the motor.
Gary

250 sport

Allen4, with that much compression on pump gas I would be very careful. At 3 psi of boost you may get away with it. I would call Dean Nickerson and ask him about your set up. If it were mine I would run one of his carbs as well. The size of the blower is a little small but at 3 psi would most likely be ok. Your boat runs great now and I would hate to see you melt it down.
Good luck-scott

jdnca1

Allan;

Do you run alum or iron heads? If they're Iron don't even try a blower unless you want to burn 100 Octane. The 731 Cam looks way to short to give any aid in bleeding down those cylinder pressures. You of all people know I'm not a blower guy, but I do U/S cylinder pressures and how to control them from all the research I had to do for my 10.5:1 motor to live 93 Octane. If you have alum heads you can go to a longer duration stick to help control those pressures and probably get away with 93Octane at 3-4psi. I would probably go with a bigger blower and turn it slower to help the problem as well. as always...my .02

Do you happen to know what your cranking pressures are?

HyperBaja

I told you earlier, get some really thick head gaskets

Turbojack

If you are interested into turning a good motor into a piece of junk then put the blower on it. I would not put a blower on any motor that is running that much compression unless using very High octane race gas. Save money in the long run & change pistons to at max 8.5, I pefer 7.5:1 & higher boost to get more HP out of motor instead of compression & lower boost & get a bigger blower.