MILD THUNDER

iTrader: (3)

Or a used car salesman.......lol

MILD THUNDER

iTrader: (3)

Pat yourself on the back though, lots of what I learned came from what you've shared. I just saved you some typing, so you can get back to work on that bad a$$ skater project.

Young Performance

Well thank you. It's nice to know that someone beside myself is reading what I type.

compedgemarine

glad to see you state this. I have wasted too much time with guys trying to explain that. they all think that because they are making 8lbs of boost they are making 1200hp with their stock crate motor because they read a magazine where someone with a small block did it. of course the magazine motor had bigger heads, a proper cam, exhaust etc. I asked some kid once what he thought his motor made and was told 500hp. I asked how he figured that and his answer was "the intake said it was good for 50hp, the headers said they were worth 40hp, etc, etc, so I added them to the 250hp I started with and came up with 500hp." I just walked away after that.

Drinkin fountian

Thanks again everyone for the advice. Im starting to get a better idea of my build now. But still not completely sure. I've got the zz502 w/ between 9-9.5 comp. (not ideal I know and haven't cc it yet) with the 320 RHS alum. heads. Thinking a 10-71 w/ 2 850 holleys and 6psi boost. I'll run a mix of 110 and 92 octane, since i'm looking at around 13:1 no big deal OR is the 2 psi even gonna be worth it. Haven't looked into cams yet but just ran across a thread talking about "exhaust revirsion" w/ a 502 and EMI manifolds, which is exactly what Im running?! What cam company or builder should I go w/ to pick my cam and talk about this with? And do u think I can pick a cam that will work for this 502 AND the 540 im building that will have all the "right stuff" to replace the 502 later.
AND I previously asked in another thread about using my 355cc pro 1 heads instead of the 320 RHS and was suggested to stay w/ the 320s. U agree? Once again, I won't be puttin alot of hrs nor be running this boat hard until I upgrade from my Bravo1.

Back4More

an 8-71 with 750's would be better.

Drinkin fountian

Im going with the 850's because I already have them and the 10-71 because when I finish the building the 540, the 10-71 will be better suited. Kinda using this 502 as a test to see if I want to stick with this blower thing for my 540 build. I am New to the power adder/ supercharger thing. Im sure Im gonna love it though?!

MILD THUNDER

iTrader: (3)

850's will work fine. IMO, Thats the carbs i would choose. Even in the Holley/Weiand catalogs, if you were buying a 6-71 or 8-71, twin 750 for small block, twin 850's for big block.

Im running 850's on top of a 468 with a 420 B&M blower. Just slightly smaller than a 8-71. Engines made 804HP non intercooled and 6lbs of boost, and run perfect. Fuel Curve is great, not even boost referenced. Idle all day if I have to. Granted, 750's would work just fine for me, but the 850's sure arent hurting a thing.

Pretty much, the theory of too big a carb causing sluggish low end and soggy performance, you can throw out the window. Roots blower like lots of carb. Or let me rephrase that, they DONT like any restriction. Ever notice the twin 1050 Dominators on a merc 900SC? Merc Racing Engineers weren't dummies. A pair of 4150 style 850's might have helped it idle a little better, over the dominators, but i'd be very shocked if they made any more power over the 1050's on that engine. (540 W/10-71 and chiller). Overcarbing ( I mean like a pair of 1150's on your setup), would most likely cause tuning issues, more than anything. Too much carb causes poor signal thru the carbs, and you end up having to run alcohol jets to get a acceptable AFR.


BDS has a calculator for blower carbs. Based on a 509CI, turning 6000RPM, running 8lbs of boost, required CFM is 1364. They dont suggest more than 30% over carb needed on a blower. so 1364CFM, +30%, 1774CFM.

You see guys all the time with big roots blower stuff. They Gut their flame arrestors, put big old Pro Stock scoops on, trying to get more air into those motors. But then they want to run small carbs.

As for the 320cc RHS heads, vs the big Darts, tough call. I don't know much about the RHS Heads. While the 320CC port size works nicely for what you're doing, you need to think about flow also. I'd Talk to someone like JIMV here on the boards. If you have both sets of heads available to you, you might be able to weld up the floors on the Darts, to get the port velocity up, and smoke the RHS heads in performance. I'd hate to tell you to run the RHS heads based on the intake runner size alone. Those Darts move some air.

Figure out which heads you're gonna use on your build, and then have Bob Madera (RMBUILDER) here grind a cam for what you plan to do. If you take your time and do a nice build, I think you'll be pleasantly surprised, and make a lot of power. You may not even feel the need to spend the extra few grand to install a stroker crank and rods. The extra 30-40ci you gain, can easily be outdone with a properly set up 509. Then you can use that cash to beef up your drive.

Pismo10

Great thread

Back4More

+1
I'm learning more... That im set up way too conservative.