Oldguard 7

Over the past few weeks I have purchased the following

Edelbrock RPM heads (64cc)
Streetfighter TH-350 Tranny (TCI recommended a 2500 stall speed converter)
Weiand Stealth Manifold
Roller tip rockers (1:6 ratio )

For a camshaft I will buy a Launati Voodoo cam ( comptemplating a 276/284 with .504 .525 lift (Edel springs allow cam lift to .575)

Im going to buy a mighty Demon carb (w/mechanical secondaries) but what size should I get? Im thinking 650 or 750 cfm.

Engine Size: 350 ci (+.060)
Inside the block I have:

TRW forged flattop pistons(w/heads, I'm hoping to get as close to 11.00:1 compression as possible).


Im hoping to get as close to 400rwhp/400 lbs/ft torque as possible. with this setup, how close do you think I'll get?

I also have a set of Dynomax headers (purchased almost 5 years ago, still in box)

Les

I'm running a similar combo in a 355- same comp. ratio w/ AFR 195s & a very similar cam (assuming yours is a solid flat tappet). I'd go with the 750 DP carb. I'm running a Barry Grant modded 750 DP with the same intake & it works very well. As for 400 RWHP, you may be hoping for a bit too much especially given the fact that you're running an auto trans. Whatever your numbers turn out to be you'll have a real potent smallblock there.

BerniesVette

Just my opinion, but I believe your setup would handle the 750 carb with no problems.
Bernie

Gordonm

I'm running a 750 DP Holley on my setup. What are your cam numbers at .050. The Mighty Demon might be overkill for your setup.

bobs77vet

why not the speed demon 650 or 750?

Taijutsu

My Sb w/TFS, air Gap, CC 218-224 HR +1.6 RRs = .530 IN/.539 EX.
I have used 750 holly w/success. The 750vs Demon was just too much carb. A 650 Demon flowed 736 cfm. For good street manners, DO NOT OVER CARB! JMHO

Rick

MotorHead

Glad to see you are trying the new Voodoo cams, they are only hydraulic flat tapper ?

If it was a Holley I would say 750Dp no problem, but the Demon is a little harder to size for me anyway, probably be OK with the 750DP

I had a similar setup with my 355ci. and could "only" muster 296RWHP and 327RWT see my new motor specs for 400/400

Nate '69

Call Barry Grant and Lunati/Holley.

I'm going with a Road Demon 625 and Holley 650dp (will test both) with a Voodoo 262/268@50 and other similar setup as you.

They were very helpful and are experts on their products.

bobs77vet

is that right? makes me feel good about my 650 speed demon..........so theres goes the gas mileage.....

Oldguard 7

Called Barry Grant. Recommended Carb: Mighty Demon 650cfm.
Will call Lunati tomorrow morning.

lars

You guys just kill me with your "over-carbo-phobia." I run a Speed Demon 750 mechanical on my 357 as my standard setup - very sweet. Yesterday, I just finished setting up, tuning and test running a Forum member's Holley HP 850 mechanical on that same 357 - it ran just great. A few minutes ago, I just returned from setting up and test running a Holley Dominator 1050 on my 357 - very nice running carb with gobs of top-end and no low-end troubles. Can someone tell me what problems you think you're going to have with a big carb that allows the engine to breathe? If the carb is set up correctly, a big carb does not cause problems. Over-carbed does not gain you any advantage, but under-carbed holds you back. Mechanical secondaries allow the driver to control to opening point and rate of the secondaries: don't drive the car like a girl, and put a real carb on it.

(I have opinions about politics and religion, too - just ask me.. )

jimvette74

You crack me up. I run a 750 holly with a stock 454ci. I will go with the demon when finnished with mod - one note though- daily drivers need a choke- especaly in cold climates.

mandm1200

There is a range of carburators that will work fine. Too small and it will hurt perfomance. How big is too big? There must be a limit somewhere or we would all be running two 1050cfm carbs. The size and type, mech vs vacuum secondary, is just another way to fine tune the engine for the way it will driven.

Bob Turner

HAHAHAHAHAHAHAHAHHAHAAHAHA!!!




Bob

LemansBlue68

Oh yeahhhh Lars??!! Well Chevy put a 780CFM Holley on their 302's in the early Z-28's and they were fast. Darn fast. So who's the "over carburetor carburetor-or", now? Huh??...and...and...My dad can beat up your dad...and...and...well... my dad IS starting to get a little old so maybe not as soundly as he used to be able to beat up your dad.....



Listen to Lars. He da man! If you're afraid of putting too much carb on your car, put a big vacuum secondary equipped carb on it and let the ENGINE decide if you're running too much carb. If the motor needs more carb, the secondaries will open; if it doesn't they won't. For chrissakes, GM put 750 CFM Q-jets on just about every V-8 they made...even the small displacement ones. What did they not know that everyone seems to know now?

Matt Gruber

some big carbs will run on the idle transition circuit at cruise, and get poor mpg, like 8.
some guys can tune, some can't.
Nail a DP at 600 rpm and if it's big and u can't tune real good, it will somtimes backfire, and a dumb tuner with the filter off may set the car on fire. Other than that, i luv big!

pws69

With your setup, I would certainly consider an 850. Why build a go-fast motor without a serious carb??

LemansBlue68

Lars has some pretty thorough papers posted in the technical section pertaining to carb tuning. If you don't know the basics of tuning, read his papers. These will give you a pretty good explaination of how to go about it.

Matt Gruber

Good Advice!
And see my homepage for even more!

lars

Glad to see you guys all realize I like to yank your chain a little bit on this carb sizing issue...

I think mandm1200 said it pretty good: There is a wide range of carb sizing that can work well on any given engine. Smaller carbs are a little easier to tune, and are more forgiving of sloppy driving habits (like nailing the throttle wide open at 600 rpm...). For this reason, the manufacturers will always recommend a smaller carb: it reduces their warranty claims and the number of calls to their tech line. Fewer warranty claims and fewer tech calls means more profit. Carb manufacturers are not in the business to make you go fast - they are in the business of making money. Keep that in mind when you look at their recommendations...

If you are not comfortable with tuning and setting up a carb, go with the smaller size. If you like to tune and set things up; if you understand basic carb setups; and if you understand how to downshift, don't be afraid to use a big carb. Just don't nail it into the secondaries at 600 rpm.... be a man and keep that rpm up over 2500..