How much is too much dual quad

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Have a buddy that ran the stock 8bbl intake on a 383 with 2 carter 625’s.
Ran fine, just wasn’t very fast.
Picked up a used Offy 8bbl...... basically no difference.

Was quicker at the track with a DP4B and a 750.

If you just want it for the looks, it should run fine if you get the carbs dialed in...... but it’s far from the best in terms of trying to make power.
 
RustyRatRod said:
It depends on a few things. Type of carburetor. Size of carburetor. Style of linkage. Progressive or straight. Two Thermoquads, for instance, although unorthodox, the engine could probably stand two 850s. Since the secondaries on the Thermoquad are regulated by engine vacuum, that means the engine will only use however much of that total 850 CFM each that it needs. Two 850 Holleys would drown it, while two 850 Thermoquads properly tuned would peel up the asphalt. Same with the Carter or Edelbrock AVS style carburetor, since they also have 100% vacuum regulated secondaries, like the Thermoquad. The Rochester Quadrajet is another example of a vacuum regulated secondary carburetor. Also, regarding the linkage, a progressive style linkage will allow the carburetors to come in more controlled a little at a time, instead of all at once like straight linkage. So unless you nail down which carburetor and linkage you plan to use, the answer is pretty all encompassing.
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so you agree, his 2 vacuum secondary 600 Holleys would run fine if tuned properly
 
I had to think about this awhile before I came up with a honest answer...

So,
“How much is too much dual quad”
The best answer I can give is that “It’s not to much carb but just not enough engine!”
 
Depends on cam duration and
Engine compression and total advance.

If you have big duration cam= no vacuum.
Might be better off with 2 480 cfm holley
Manual secondarys.

I have similar set up on 67 cuda 383 11:1
Open chamber steel heads ported.
550 lift 300 duration. 1.6 rockers solid cam
Have no vacuum. 50 Degree straight advance .2 480cfm Holley 50 cc pumps.tunnel ram
Can't get it running any better.....

Also without 3.91 gear or better you will lose little low end power for sure
 
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Dang, got busy for a bit, here is the coupling video of my previously excellent running engine with twin AFB Edelbrock 600’s On my solid cam 360. Simply jet accordingly. Done.
 
Once upon a time, when I was young, I had a 72 Monaco with a 383 69 Road Runner "spec" engine, that I installed a Chrysler dual 4 manifold on, and two edelbrock 625's. 14 trials for jetting test/tune till something was averageable acceptable for a driveable car. This thing got 21 mpg Cdn. Was the stock cast 4bbl more useful? Was the Edelbrock single plane more peppy, sure. But what was more "cool"!
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Figure approximately 1.5 x CFM of a single 4bbl on a street motor and almost 2 x CFM on a race motor looking for a performance improvement from proper single carb flow. A friend took a Strip Dominator and 750DP Holley off his healthy 340 Barracuda 4spd, replacing it with a tunnel ram and 2 x 450cfm tunnel ram Holleys. He promptly cost himself .5sec ET. He was trying to salvage the situation, and I was wanting to try a 750DP like he was running on his single setup, so I told him to sell the 450s and get another 750 to exactly match his and I'd buy it 100% if it didn't help. Yep, 1500cfm on that tunnel ram worked on the radical little 340, and he knocked a whole second off the 450s!! Who knows, it may have wanted only 1300, or maybe 1100cfm, but 450 x 2 (900) couldn't beat a single 750. Your results may vary. I have personally ran 2 x 660s on a 383 with magical results and 2 x 850s on a 471 to good result. In the future, I want 2 x 1150s on a 526" B1 tall deck. We will see!
 
I run a pair of 800 cfm AVS2's on my 440 with tunnel ram. Runs great on the street, and I'm approaching low 11's / high 10's in the 1/4 mile. Having an AFR gauge, and reading

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plugs makes tuning pretty easy.
 
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