Carb recommendations

[HP_Cuda]

I see alot of folks giving recommendations on carb sizes without knowing the science behind them.

What you need to know is Volumetric efficiency. Yes you can put a 800cfm dominator on a 318 small block but you will be very inefficient and will have paid for a carb that is overkill.

VE = (3456 x cfm / cid x rpm)

So just for fun I've built a chart for different Mopar engines with a max rpm of 6000:

Cubic Inches            Carb Size recommended
318                           600cfm (needed 555cfm for 100%)
340                           600cfm (needed 590cfm for 100%)
360                           650cfm (needed 625cfm for 100%)
400                           700cfm (needed 700cfm for 100%)
426                           750cfm (needed 750cfm for 100%)
440                           770-800cfm (needed 765cfm for 100%)

A good VE calculator is here if you want to play around and change the variables:
http://www.ajdesigner.com/phpengine/engine_equations_volumetric_efficiency.php

I'm partial to Holley carbs as I have rebuilt many of them and know the ins and outs of them.

B

[Chryco Psycho]

The theory is good but it doesn't work ..... my 440 ran OK with an 850 DP holley on it 12.4 in the 1/4
I upgraded to a 950 Vacuum & dropped to 12.2 , so I installed a 1050 dominator & the car went 11.7 .
 the Factory used 850 TQ carbs on 360s no problem & the 950 6 pack on a 340 so either the carbs are overrated or the theory is flawed

[HP_Cuda]

Tell me how you built your 440?

The theory is good but it doesn't work ..... my 440 ran OK with an 850 DP holley on it 12.4 in the 1/4
I upgraded to a 950 Vacuum & dropped to 12.2 , so I installed a 1050 dominator & the car went 11.7 .
 the Factory used 850 TQ carbs on 360s no problem & the 950 6 pack on a 340 so either the carbs are overrated or the theory is flawed

[06Daytona]

I've seen a calculator like that somewhere that took into account cam specs, rear end, tire size and a few other variables that seemed to be pretty accurate. Using a 440 for and example the carb size was anywhere from 750 to 1200+ depending on boatloads of variables

[Road_Runner]

Mopar Performance recently did a carb comparison on their mildly built 383 test motor.  If I remember right the best carb was a non HP 850 double pumper.  Smaller than that, they gave up as much as 50 HP in their test.  I agree that for most street driving a smaller carb than may folks try to run on the road is better, but for 1/4 mile or top HP it appears bigger is better.

Later, Jim