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The poster has been told both by myself and the tech he spoke with yesterday that this carb is too big for his 440 as it will flow over 1000 cfm.

It is NOT going to run right on this combination regardless of tuning and belongs on something 500 inches or larger to which we were told that they would post we did not fix the carb. Go ahead as I believe we have gone way above what was required to begin with in this situation.




You care to explain why? I personally have run much larger carbs than this on a 440, and picked up a ton.
This past weekend I swapped out a 850HP holley and threw on a old 9375 1050 3 circuit dominator and the car picked up more than I would have ever dreamed.

That carb looks like a 850 Speed Demon Correct?
I know BG likes to select and choice carbs based solely on camshaft overlap, and engine size. But to say it flat out wont work is a bold statement. Im sure this will get technical with dynamic flow property jargon, how low vacuum signal will not emulsify the fuel properly etc...But the fact is people have been doing just this for decades with Holley carbs, myself included.
Care to explain?

BTW
I solute you for what your trying to do....
Thanks
Bob

That part of where the problem begins in that our stuff will flow a lot more then the Holley counter parts. The 850 Holley flows pretty close to that number and is a good size for a 440 but our 850 as pictured with the down leg boosters will flow a little over 1000 cfm.

You are correct in that it can get real technical because it does involve signal and the ability to pull fuel through the booster but I'll simplify it with an example. Take one of the sand hour glass deals that you turn over and the sand passes through it. It is wide at the top and narrows in the center, this can be compared to how the venturi shape and size works. It takes a little time for the sand to pass...correct? Now imagine opening the id on the center where it narrows a good bit and watch how the sand passes through it. On a smaller carburetor it has more od an hourglass shape to the venturi which keeps the air speed up which in turn keeps the signal strong. As you make the venturi larger [aka our 850] the point at where the venturi narrows is much flatter so on the same size engine as the smaller carb the signal would be slower causing it not to pull enough fuel thus why we want to see more cubic inches as we get larger.

Signal alone though is not simply controled by venturi size which is why some of you guys can get away with larger carburetors on smaller engines. Other factors like compression , cyclinder head size and flow as well as the camshaft and engine rpm all have to be taken into account. Other things like vehicle weight , trans , converte tire and gear size also. A lighter car can get away with a bigger carburetor because the load is different thus having a different signal.

You were also correct in that our carbs are rated around duration as well in that as the duration gets larger the amount of signal can decrease so the calibration and even in some cases the location of the bleeds have to be changed to compensate for this.

Technical Support Barry Grant, Inc. www.barrygrant.com