how much head flow to justify dually carbs?

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Bad Shrimp

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(2) questions..........I currently have zero need to know,,,,just trying to learn a little mo etc........anyhow

How much air do my/their/them/your heads need to flow to actually make use of or need dual 4bbl carbs?

Once my/their/them/your heads are flowing that amount is their a benefit of running...lets say for example dually 500cfm 4bbl's vs single 1000 cfm 4bbl?

Bad Shrimp

:hiding:
 
Working with multiple carbs is an art.
I'm 52yo and been handy with it my whole life.
If you or any of your mates are inexperienced with multiple carbs then be prepared for a lot of pain before you see any gain over a single (easy to work with) 4bbl.
When you go multiple you'll be running more cfm than what sounds right for a single 4bbl.

Example : my 440 barracuda has 400hp and had dual 500 edelbrocks on it originally.
A single 850dp would have been more than adequate.
I then swapped out to dual 600vac holleys.
Since then I've built a home made mechanical sixpack with dual 350 2bbls as the primaries and a single 650 2bbl as the secondary(thirdary?)which totals 1350cfm but comparing the 2bbls to the 4bbl vacuum draw they come in around 950cfm total.

Tuning is the biggest issue.
Make sure you've got someone who knows what they're doing.

And just out of interest : many years ago I set up 6x 1 1/4" SU's on a six cylinder inline Ford engine for a mate.
Along with many triple weber,triple SU and twin downdraught carbs on slants and aussie hemi sixes.
Even ran alcohol through webers.
 
Until you get into high horsepower applications and things like tunnel rams you're likely better off with a single four. Dual fours were a necessity when all four barrels were small, now for most folks it's mainly for decoration. With that said, I do have a factory iron dual four intake for an RB (original 413 intake). I don't know if I'm trying to talk myself into or out of using it........
 
340 8bbl has a pretty nice running TR equipped 340.

DJV had one too.

Takes time to sort them out, but, they can be run on just about any SB/BB mopar with proper tuning.
 
I ran a tunnel ram and a nice set of 660 center squirters on a 451" RB, swapped it out for a modded 850 and picked up almost 3 tenths in the 1/8th mile.
 
i was always a firm believer in one big carb. but then i got into the really old stuff and multiple carbs are just common place, they didnt have 4 brls back then and liek jim said when they did they werent that big. i had a rover v8 for my coupe i never got to put it in but i set it up with 2 rochster 2g carbs on an offy intake i ran it on a test stand it it ran really good. had awsome throttle response and a nice idle. i was surprised how well it worked being only a 3.9l. i have since been thinking of a 2x4 setup for my dart, but i need to stop messing with it and just drive it.
 
How much air do my/their/them/your heads need to flow to actually make use of or need dual 4bbl carbs?
Back in the days of limited size carbs (like the early 60s with 400cfm WCFBs, or in the 60s before Dominators) there was a size need. But really it scomes down to signal strength much more than airflow. Two smaller carbs may be more responsive, or be able to be staged so the egine doesn't act over-carbed at low speeds or to improve idle quality. Now I think it's much more a visual/preference deal. As there are so many large singles available and for most people they are less complicated than dialing in two.

Once my/their/them/your heads are flowing that amount is their a benefit of running...lets say for example dually 500cfm 4bbl's vs single 1000 cfm 4bbl?
Using modern intakes and carbs, no. No performance benefit IMO.
 
I ran the weiand street ram on 2 seperate BBs with 600 holleys, One was a 451 lowdeck, the other a mild 440 with stock replacement pistons, the 451 was unstopable over any other single carb i tried, just this pst year it got a pair of 660s & the power is even better all across along with the 60ft., It gained close too 2 mph & dropped a solid .2 over the 600s. The 440 had tons of torque as long as you stayed out of the secondaries, I'm guessing the compression & volume didn't match up, i'm sure a pair of 450s or 500s would've been better, but either way, both these engines had irons heads, Low end torque IMO was better then a single carb. Those were my results, others may very.
 
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