Thread: Carb Advice Needed!

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Ok got a SBC 383 stroker.....comp cam intake 283/281 Exhaust, .603/.600 in. Intake Lift, .590/.587 in Exhaust. AFR aluminum 1110 heads. 220/65CC intake Runner Volume (cc): 220cc, Exhaust Runner Volume (cc): 80cc. Super victor intake manifold.

I dont want to be like all those other cats and over carb. I have too many conflicting opinions. (I know EFI ASAP!!! Maybe next year) Just some help from some guys that have been there is whats needed. Many Thanks in advance.

Originally Posted by Screwby

Ok got a SBC 383 stroker.....
I dont want to be like all those other cats and over carb. I have too many conflicting opinions. (I know EFI ASAP!!! Maybe next year) Just some help from some guys that have been there is whats needed. Many Thanks in advance.

Morning Screwby, It's good to see you here and welcome to the club.

The old rule of thumb for CFM of car was twice the cubic inches. If you wanted to make things more responsive ( and you weren't trying to squeeze every last HP) then you went down to the next closest number available.

So 383 x 2 = 764 (next closest number will be 770)
for a street motor I'd prefer 700, it'll usually be "crisper" and more responsive.

Originally Posted by Screwby

Ok got a SBC 383 stroker.....comp cam intake 283/281 Exhaust, .603/.600 in. Intake Lift, .590/.587 in Exhaust. AFR aluminum 1110 heads. 220/65CC intake Runner Volume (cc): 220cc, Exhaust Runner Volume (cc): 80cc. Super victor intake manifold.

I dont want to be like all those other cats and over carb. I have too many conflicting opinions. (I know EFI ASAP!!! Maybe next year) Just some help from some guys that have been there is whats needed. Many Thanks in advance.

Please explain to us what the motor will be used for, what vehicle it will be in, the anticipated rpm limit, what transmission will be used, what stall converter if auto and what rear gear ratio. Can you furnish the piston part number? Thank you. And most importantly, will the vehicle be street driven?
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I think tunnel ram with dual center squirter 660s on 850 throttle plates mounted side ways would be the way to go-------------you'll get more attention at shows instead of getting tickets for driving insanely to be noticed-----------leave the case of beer in the trunk for traction instead of evidence in the back seat-------

Oh-------Merry Christmas---gas prices are up

Originally Posted by techinspector1

Please explain to us what the motor will be used for, what vehicle it will be in, the anticipated rpm limit, what transmission will be used, what stall converter if auto and what rear gear ratio. Can you furnish the piston part number? Thank you. And most importantly, will the vehicle be street driven?
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Firstly, thanks to all. I knew this was where I needed to go. Street driven. I have a 700R4, 3,000 stall, 411 posi.

Originally Posted by techinspector1

Please explain to us what the motor will be used for, what vehicle it will be in, the anticipated rpm limit, what transmission will be used, what stall converter if auto and what rear gear ratio. Can you furnish the piston part number? Thank you. And most importantly, will the vehicle be street driven?
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Also now which one?? Quick fuel seems to be the go to?

Ok got a SBC 383 stroker.....comp cam intake 283/281 Exhaust, .603/.600 in. Intake Lift, .590/.587 in Exhaust. AFR aluminum 1110 heads. 220/65CC intake Runner Volume (cc): 220cc, Exhaust Runner Volume (cc): 80cc. Super victor intake manifold. Street driven. I have a 700R4, 3,000 stall, 411 posi.
I dont want to be like all those other cats and over carb. I have too many conflicting opinions.

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Well, this looks to be a balls-out street race motor where bigger is better. A healthy 355 will need a 750 to make max power and it stands to reason that a healthy 383 would need an 800 to make max power. You have enough cam and more than enough heads to make power to 6300. I've put a lot of motors on the software dyno over the years and I can see this motor making 115% efficiency pretty easily, so using the formula CFM = Cubic Inches x RPM x Volumetric Efficiency ÷ 3456, I can see 802 CFM working out well. With a 3,000 rpm stall converter, I would use a full-mechanical double pumper, leaving the manufacturer of said item to be determined by you.

You did not provide the piston info, so I can't figure your static compression ratio, so I don't know if the motor will be friendly with pump gas or not. If you have not completed the assembly of the motor yet, cut the block decks to arrive at a squish/quench of between 0.035" and 0.045" to help prevent detonation on pump gas, using a 0.039" to 0.041" composition head gasket to prevent fretting of the aluminum cylinder heads. Ideally, the cam will want 9.75:1 to 10.0:1 static compression ratio.

Note for the other members of ClubHotRod who have not used a 4-pattern cam yet.......
Screwby has used a CompCams 4-Pattern cam in his motor. This is the first of its kind that I have seen in the forums that I frequent, so it takes a little explaining.

When you're using a single-plane intake manifold such as a Super Victor, you can divide the motor into two different cylinder groups. There are 4 cylinders that are closest to the carburetor (3, 4, 5, 6 on a Gen I SBC, called the inboard cylinders), and 4 cylinders that are further away from the carburetor (1, 2, 7, 8 on a Gen I SBC, called the outboard cylinders). It stands to reason if you think about it, that the outboard cylinders fuel and air requirements would be different than the inboard cylinders fuel and air requirements.

For years, cam grinders have used a 4-pattern cam on NASCAR motors and now the technology is showing up for street motors as well. That's the basis for this young fellow's motor, a 4-pattern cam using 1.8:1 rocker arms. Here are the specs on his cam and some remarks by Comp and Summit......

08-604-44 - 4-PATTERN O.E. Hydraulic Roller Camshafts

https://www.summitracing.com/parts/cca-08-604-44

In addition, here's a tutorial from CompCams......
https://www.youtube.com/watch?v=3aL_G2GM3zM

Me personally, I would not be using an overdrive trans in this combination. OD transmissions are for fuel mileage and require a much milder cam than what the OP is using here. This cam, at its sweet spot, will be revving higher than what an OD trans needs to run at to make fuel mileage. I would have used a well-built TH400.

I would also not have used a Super Victor or the cam that the OP chose because the dual-plane, high-rise intake that I would have chosen would not need a 4-pattern cam. The OP is counting on max power at max rpm's, but on the street, that's not how it works. You need to be making max power from 3000 (or wherever your converter stalls) to 6500 and that is where a dual-plane, high-rise intake manifold shines. The OP will be down on power from mid-range to top end by using the Super Victor. This has been proven many times on the dyno. If the OP were using a 6000 stall converter and a cam that would pull to 7500/8000, then I would agree with using a Super Victor.

Building a fast car is about building a fast COMBINATION of parts that rely on each other.
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He already has a set of Airflow Research #1110 heads and they are VERY GOOD HEADS.
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In post #7 he says street driven--------and also he lives in Denver------needs higher static compression or a supercharger and also since air is thin needs bigger carb size to allow those heads, etc so enough air can get into the engine------IN THIN AIR you got to do as much as you can to feed the cylinder---------

Thats the reason some whiskey is only 86 proof??????

Good point about the altitude Jerry, I missed that. Now that I live at sea level, I assume everyone else does too. ..... 9.0:1 with a turbo or sneezer might be the hot tip.
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Compression ratio would remain the same, because it is only a mathematical computation, but cylinder filling would be about 20% less due to a decrease in atmospheric pressure at altitude.
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Originally Posted by DennyW

Yes, compression ratio would be the same, but, the cylinder compression pressure would not.
Example: If your compression pressure was say 150, and you went to Denver, it would be about 120.

Exactly. Thanks Denny.
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Two different suggestions for you would be a quick fuel brawler 750 double pumper if your vehicle weight is not to heavy and you can pick up rpm's very quickly or a quick fuel brawler 770 vacuum secondary. Either one would be what your engine can use and 20 cfm won' make any much of difference for tune wise. Don't get a holley brand street avenger vacuum secondary as it will be to lean out of the box and you would have to modify it to get a richer fuel calibration for the idle circuit and the quick fuel brawler carbs are cheaper but better quality out of the box wise and you can tune everything on them just by putting in different idle feed restrictors and you can also change air bleeds and also the power valve channel restrictions as well and they are really nice carbs.

I am building a nice 377 dart shp build (4.155 bore 3.480 stroke) 10.1 CR but with a milder cam and I use a double pumper carb with a turbo 350 and a 2500 stall so don't be afraid to use a double pumper as they can work with automatic transmissions just fine if you can pick up rpms quick and the engine does not lug any. The vacuum secondary though is the most forgiving on the quick open wide open throttle secondary operation but I don't think you would have that issue with a good tune.


https://www.summitracing.com/parts/q...7257/overview/

https://www.summitracing.com/search/...fuel%20brawler