Is a 750 cfm carb big enough to support 500 hp

if it was set up rite it may but if it were me i would be lookin at a 830 cfm carb..

I may be wrong on this but I think its going to depend on what kind of intake your running. Dual planes typically run a bigger carb than a single plane. On my engine I'm making around 525 hp and I had Prosystems build a carb for it and it flowed 830 CFM. I'm running a dual plane. Also if your looking at holleys the number such as HP950 is not a 950 CFM carb. It will flow 850 CFM. When you order your carb make sure your getting the actual flow rate !

It's a dual plane. I have a 750 and a 800 looks like I should go with the 800 cfm

You need an 800cfm for 500hp.

2bbl engines are in getting into the mid to upper 400's now, but they are severly restricting the engines they are on.

So......yes a 750 can support 500hp, but it will be restricting it meaning a larger carb can make more hp on it.

Remember, Merc used a 800DP on the Merc 500HP.

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What Endeavour said above is true. A dual plane will need more carb than a single plane. A dual plane only lets each cylinder see air/fuel from 2 throttle bores. A single plane let's each cylinder draw air/fuel from all throttle bores.

Also, single planes usually have more plenum volume and all runners are open to each other.....meaning it has more storage area than a dual plane.

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So, what would be better for us to answer your question would for you to post up your engine build and we can better help pick a carburetor for you.

Is the Edlebroc air gap a dual plane?

You need to base CFM on Cubic in and max RPM. In carb selection smaller is better. Look at CFM charts on Holleys website for best choice or call them. 750 is more than enough. You will waste more time trying to tune the carb if you go to big, than it is worth. Get it right to start with and it will work out of the box. Try BLP in Fla. 800 624 1348 ask for Rick

+1 750 is more than enough @ 500 but going a little bigger sure won't hurt. I think you'll be fine either way. The 750 should be easier to tune.

A 750 is "big enough" but an 800cfm will still make more power on the dyno at the top end.
I ran an 800cfm HP500 carb on a 425hp 454 and it was fine and not hard to tune.