Hey Stephen, for the new 383 I've decided I wanted a Demon, but I'm still torn between what size cfm to get.

Many people tell me that less is more and you really don't need all that much, but I see that you were using a 850dp on your 383.

I'm looking at anywhere between 400-450 horses N/A, but I plan on giving it quite a large shot of nitrous (200+) so I was wondering what your opinion was on the carb cfm?

Thanks.

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82 Z28
350 carb'd, Edelbrock Performer RPM package (minus heads), Hooker Super Comps, Mufflex 4" offroad y-pipe, 700r4 with B&M shiftkit, '85 IROC 10 bolt rear with Richmond 4.10's & Auburn posi unit, Lakewood 50/50 drag shocks. Shooting for 3000lbs w/ driver.

The car's website

(NO2'd 383/TH350 buildup this winter)

AIM: fillup82Z
ICQ: 77979548

 

I run a 750 vac sec on my 427 (actually 433). Even with VE%'s over 100%, max 660 scfm at 6000rpm. The dyno sheet is on my page if you want more info.

Two of the biggest mistakes people make when building a motor is too much carb and/or too much cam, especially for the street.

Just my .02
Miles

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88 427 Camaro
12.18 @ 113mph 1.75 60ft
http://www.geocities.com/mek88427

 

Miles, your $.02 means a lot to me...I was just a little concerned that with all of the extra nitrous being added, I didn't want the carb to fall short. I love your car. Once it's all said and done I should be over 600 horses with the nitrous, so would a 750dp be too much still or just right?

 

The 850 worked fine on my engine. It depends on a lot of things that a simple formula can't tell. I probably could have easily used a 750 but when I bought the carb I was thinking of going to a big block at the same time so I was thinking ahead. The 850 should work great on my new big block but I may have to buy the K&N StubStack to boost it up to about 880 cfm

Chosing a carb size is "almost" a guessing game. I know of a T-altered with a 377 and a 650 CFM carb that runs high 9's. I've also seen a 350 with a 1050 dominator run 10's. Usually it will depend on your engine red line. An engine that stops at 6000 doesn't need as much carb as one that goes to 8000. When you consider a street engine doesn't get much above 5000 rpm they can use 600 cfm carbs (or less) with no problems.

You could also buy a Race Demon with removable venturi sleeves from 675 to 1050 cfm. That way you can change the sleeves instead of the carb. You could also buy a King Demon (demon version of a dominator) that also has the removable sleeves. It can be made as small as 795 cfm and as large as 1295. Running at 795 would work well on a small block and it would have the "drool appeal" of running a huge dominator carb.

One more thing. When I bought my DP carb I knew it was going to be "race" only. I wasn't concerned about milage or low end performance such as driving on the street. My powerband started around 3500 rpm.

On a race weekend I would usually go through 5 gallons of fuel and would do about 10-20 miles. A 750 would have probably given better milage.

[This message has been edited by Stephen 87 IROC (edited November 06, 2000).]

 

Correct me if I'm wrong, but if you're using a wet-plate nitrous system, it's going to be below the carb and the size of the carb above it won't make any difference.

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1984 Silver Z28, 383 cid 4 bolt, ARP Fasteners, 2 1/2" Cowl Induction Hood, 600 cfm Performer Carburetor, Torker II Intake, Performer RPM Heads, XE268H Cam, Magnum Roller Tip Rockers, MSD6AL Ignition, Blaster2 Coil, Recurved HEI Distributor, 700R4, TransGo SK, 2.73:1 Limited Slip Dana 44, Terminator Headers, Custom 3" TIG Welded Stainless Exhaust, Flo-Pro Twister Muffler, 4 Wheel Disc Brakes, Oil Cooler

 

Correct. Any nitrous system setup doesn't care what size the carb is. All NOS systems provide their own extra fuel when the nitrous is injected. The carb couldn't feed enough fuel for a NOS system.

A carb is adjusted to provide 14.7:1 air fuel mixture. When NOS is injected, it's an oxygen rich mixture. With this increase in oxygen it also needs more fuel for a 14.7:1 mixture. The carb won't change so the NOS system provides the necessary fuel mixture. NOS and the extra fuel are both fed through replacable jets to adjust power levels and fuel mixtures.

When you see NOS meltdowns it's not because of the NOS but lack of fuel. Running way to lean will melt pistons real fast.

[This message has been edited by Stephen 87 IROC (edited November 06, 2000).]

 

Like already stated above, an N20 system (on a carb setup) brings its own air and fuel to the party.

You should run a completely separate fuel system (pump and all) for the nitrous.

Miles

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88 427 Camaro
12.18 @ 113mph 1.75 60ft
http://www.geocities.com/mek88427

 

Alright, thanks guys for the info. I appreciate it as always. I should of been more clear as to my plan.

My rpm range will be between 3000-7000, at least from what I gather at this point. I also am going to use a controller for the nitrous so I can start off with a small shot (50hp) and gradually work up to the full 300hp with the NOS Sportsman Fogger system.

With the extra torque of a 383, I'm probably going to get the Super Victor single plane intake that have the nitrous bosses on it to make my life easier with the fogger kit.

The 795cfm dominator sounds very cool, but that's seems like it might be a little overkill on my setup?

This technically can be driven on the street, but it won't be driven that often, so things like high idles and high gas consumption aren't big worries of mine. If I wanted to use it as a daily driver, I wouldn't of taken out the heater and wiper assembly

Forgot to add...Miles, you got me thinking about a seperate fuel system for the nitrous. Would a separate 5gal fuel cell mounted in the engine bay be out of the question or a nice way to make sure I have enough fuel?

[This message has been edited by crazeinc (edited November 07, 2000).]

[This message has been edited by crazeinc (edited November 07, 2000).]

 

That's what we have on my friends Cuda. It is a 1 gallon fuel cell mounted in the left front corner with a fuel pump and regulator right there also.

You don't need a very big fuel cell for the nitrous side. On a typical mid 8 sec pass, we run a 500hp fogger kit and use around a quart of fuel (from the nitrous tank).

On the bottom of my page, the first three pictures of the Cuda show where the regulator is. The tank (not shown) is mounted just ahead of that and the pump is underneath.

I will take some better pictures and try an post them next week.

Miles

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88 427 Camaro
12.18 @ 113mph 1.75 60ft
http://www.geocities.com/mek88427

 

thanks Miles...the only concern is that there are gas tanks in the front and rear of the car now, so no matter where I get hit, I could possibly explode Does your buddy with the Cuda have a special roll cage or something made for that or is it just bolted to the frame?

 

Just bolted to the frame.

Miles

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88 427 Camaro
12.18 @ 113mph 1.75 60ft
http://www.geocities.com/mek88427

 

Just 2¢ more to add,
If a plate system is used, you are usually better off with a smaller carb as opposed to the oversized one. The reason being is that the smaller venturies will be flowing air at a higher velociy and that will help atomize the nitrous/fuel mix better as it sprays into the plenum.
A smaller carb is usually better on a fogger system as well, not so much for atomization of the n20/fuel mix but because you will have better throttle response & torque out of the hole. Then as the nitrous comes in you get more air(nitrous) & fuel through the foggers.

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• 355 cid
• AFR heads
• Arizona Speed & Marine hydraulic roller cam
• SLP runners
• TRW forged pistons/ceramic coated
• fully balanced
• Edelbrock headers/ceramic coated
• SLP cat-back
• Paxton supercharger
• Nitrous Express nitrous oxide

My IROC-Z

 

I'm 99% sure on the NOS Sportsman Fogger kit w/ an Edelbrock Super Victor intake with the nitrous bosses on it. The Pro Shot Fogger is tempting, but I don't think I'm crazy enough to go over a 300 shot