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Discussion Starter #1
Here are my specs...

351w (30 over/357.2), world heads that are ported, headman headers, comp cam (int lift .493, exh lift .5)/hyd lifters/roller rockers, edelbroc performer RPM intake, c4 tranny w/ 2.5k stall, and posi/4.11 gears.

Currently I have a 4bbl 650cfm holley vac secondaries carb. Is this the right size? How should I go about moving foward with tuning the engine to the correct fuel amount?

Based on this formula

(ENGINE SIZE * MAX RPM) / 3456 = MAX CFM

I have..

(357.2 * 5500) / 3456 = 568.46

My current carb appears to large.. am I doing something wrong?

Suggestions?
 

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I'm setup pretty close, except for the 4.11's. I'm only running 3.25's, but I don't think it will matter what size carb.

I'm using the Holley 650 double pumper with mechanical secondaries. Seems to be enough carb for me. What ignition system are you using? I'm using the MSD system(distributor, box, and coil). Something to look into.
 
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Discussion Starter #3
your 650Vac sounds fine. if your having carb problems can just be some simple tuning jet sizes. Is it running lean or rich?does it bog?is throttle crisp?
 

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Nice combo....balance *G*

Carb is fine...just read the plugs and do a bit of tuning and have fun!

I run a 780 on similar combo (more CR and cam) in the race car....different application though so I'd say that size might be a bit big for you.
 

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The key point is this: if it's a streeter, you are doing it the right way by figuring out what you ought to have on it. 650 sounds right. Too many kiddies got too big. I built a 377 stroker motor and used the same size carb, it's quite nice for throttle response, fuel milage and just driving around. However, if your car is strictly a drag/bracket car or a high speed track car you may want to go bigger. Remember the "if" part though.
 
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Hate to break everyones heart but this arguement is going on at another forum I'm on, here's my experience(20 years). My 429SCJ runs its best with a TUNED Dominator, .2 over a custom 935 & another .3 over a 735 vacuum. The last 351 I tuned had WP's & a 292H Comp, ran & drove it's best with a 1050-9375 Dominator. I have dyno pulls to prove it. Problem is no one ever tunes one, they boly it on & when it ultimately fails, too big. I have run a stock 429SCJ with 2 1150's & I never saw a stock engine haul a$$ like that. Call me crazy... everyone does, I do have 25 years of racing & tuning to back this up. It's usually just easier to go ahead with the smaller carb as proper tuning takes time, experience, & money. BTW the 357 we ran only went in the 10's with a Dominator. 11.50's without it.
 

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I never argue with experience and dyno sheets. *G*

I just bought a new Edelbrock 750 from a fellow VMFer that I'm going to try out on my 331 stroker. I'll be using some Edelbrock heads (2.02/1.60), Weiand Stealth and the Comp Cams XE274 or 284H. I intend to do the chassis dyno and tune with both a 750 and 600. Then make my choice.
 
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That's the thing.. how do I tell if I am running lean/rich? I want to get the best responce out of the engine from 0mph. The goal of the car is to eat as much rice as possible /forums/images/icons/smile.gif.
 
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Discussion Starter #9
I have MSD wires, with a nice coil, the dizzy has an electronic points system which was used to replace the stock system.

Oh yeah.. it's vac adv too.
 

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You only turn it to 5500? Come on, live a little!!! I'm running a 428 Cobra Jet carb(735 cfm) with almost the same set-up. I run the World Product Sr. heads, Comp 292 Magnum, Torker 2 intake, gear drive, Mallory Comp 9000 Unilite dizzy, 3.50 gears and my plugs look like I just put them in(about 3000 miles on them).
 
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Discussion Starter #11
Why go higher?

Based on the desktop dyno software I do not need to rev beyond 5500.

Justen Stepka
 

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This is what/how I calc CFM

CID times max RPM times volumentric efficiency divide by 3456 (BP)

CID: 357
RPM: 6000
VE: 90% (a little high for street engines but thats how I like to calc it)

CFM= 557.8

However, with all your mods, I would allow an additional 20% flow which calcs out at 669.36 for a 4V single pumper carb. Looks to me you're right on the money!
 
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