Sorry if I came off pissy... that was not my intention. Thank you for the information. The intake from clifford can use two or 4 barrel carbs depending on which adapter plate you get. I do have a question about CFM. I get the less is more explanation for carbs for smaller displacement motors, but...... How come guys are getting away with running two 2 barrels on a 223. That would be over 500 CFM. Maybe they are just not using the carbs to there full potential?
We're all good man, just want to be sure
I don't come of smart, it's never my intent.
The deal with carbs is, they are just a straw in an airstream, the air pulls fuel out of the straw by the low pressure caused as it passes over the straw tip. The more air flowing through the venturi, the stronger the fuel signal and the mixture is controlled more accurately. Additionally the faster flow (small carb vs large) causes the fuel to be broken up better. Thus there's always a compromise between using the smallest carb for best response and economy, and being big enough to supply max power. This tug-of-war is why progressive-opening 4V carbs were created.
When a big carb bogs, it's because the airflow is too slow to pull any/enough fuel from the jet and up the straw, the engine goes way lean. Sometimes guys think it's the other way round, "she won't take the gas!" No, the bog is a lack of gas not too much, because there's too many barrels open, the air is barely moving and can't pull the fuel to the top of the straw. The fuel that does come out is in globs because of the lack of shear in the slow air, economy and balanced distribution are reduced.
A 223 cu in engine at 80% volumetric efficiency breathes: 103 cfm @ 2000 rpm, 155cfm @ 3000 rpm, 206 cfm @ 4000 rpm, 258 cfm @ 5000 rpm.
The 280 cfm 2V carbs used in the pre-emission era on 300-307 cubic inch stock V8's produced 210 HP and 310 lbs of torque. In a 4 barrel rating, that's equal to a 196cfm carb- making these power numbers. For
all normal street driving, a small carb's advantages outweigh the gradual loss of maximum potential power at high rpm- in my humble opinion.
If our engines were rotary pumps with a steady-state air demand, the above numbers would be the end of the story. Any carb bigger than the numbers above would be a waste of carb size, it would never be used. Since they're a piston pump which draws nothing aprox. 70% of the time, then suddenly gulps in a breath, the whole concept gets almost infinitely complex, as fluid dynamics is complex. Multiple pressure waves bouncing around in the intake, and we're drawing in two fluids with different densities. AFAIK there's not a fixed formula for how much bigger a carb needs to be than what the max gross airflow volume is. Camshaft, plenum volume, street or race application, etc all affect the size of the ideal carb. Regardless, the mindset of too much carb being necessary for modest street engines is the norm, and has been for a long time. On a stock or near stock cam engine used for legal on-street driving, a carb with a rating near the cubic inch will have the best street manners and economy. And no slouch on power. 200 HP and over 300 lbs of torque moved a heavy Buick or Chevy just fine @ 280 cfm, a cfm rating 9% less than the cubic inch of the engine.
On your 223 with your good intake, a 350cfm 2V or a 390 cfm (Holley) or 450 cfm (Quick Fuel) should be near ideal. Any thing bigger than that is not going to gain on the street. A 4V gives the advantage of the small carb efficiency during calm driving, then the additional "second 2 barrel carb" for WOT power and rpm. The vacuum-controlled secondary type will perform better, since it regulates throttle opening to air demand. The Edelbrock 500 cfm would probably bog when the back barrels come in, on that small engine. The Quick Fuel has more tuning features than the Holley, particularly the adjustable vacuum control of the secondaries. This carb would be first choice were I looking for a 4V for our small sixes. It's also very reasonably priced, relatively speaking.
https://www.summitracing.com/parts/qft-sl-450-vs
