I know this question is a shot in the dark sorta, but ball park, what will say an 850 cfm carb support in a N/A motor with a 7,000 rpm limit.... max horsepower ?

The HP difference between a 750, 850, 950 or larger isn't going to be very great. How well a carb performs depends on how when the engine operates through the rpm range. Bigger carbs are more consistant however smaller carbs offer better throttle response.

For a street car, bigger isn't better because the engines operate at much lower rpms the majority of the time. A race car such as mine is designed to operate at high rpms where the engine makes it's most power. After I launch, my rpms don't drop below 6000 rpm until the finish line. It's hard to over carb a race engine. I run two 850's on my engine. On the other end of the scale, a NASCAR restrictor plate race has holes in the restrictor plate that would make a 600 CFM carb look good but they still produce 600+ hp and run consistant 180 mph.

While a modest 650 is enough for a typical daily driver 454 BBC, I've also seen two 1050 dominators on a 434 SBC race engine.

Back when I had a 383 stroker and when I still ran a single carb on a 469 BBC, I was taking the engines to 7000 rpm with only an 850DP.

850 is more than enough i would go 750

try this free calculator, it is kind of cool
Virtual Engine Calculator Free Download

Yes, I tried that one, looks like you only get good info if you buy it and know your VE exactly

Carb calculators are only good for factory style street engines.

yeah screw those carb calculators, they'l leaving you scratching your head. i run a mighty demon 750 and rev past 8,000. also depends on your compression and fuel, i run a race/pump mix other wise i was going to go with a 650, however my compression is in a funny place. 7,000 isnt anything crazy for a small block, im sure a 650 will be just fine. keep over carbueration fresh in your mind, too big is bad

I wonder alot if I overcarbed my 496 with the 1250 - But I get sick of buying everything 2-3 times.. I figured If I am giving up 10 ft lbs, I'll live with it.

HAhaaa ... no proplem rpm`ing that one eh?? I think I`m going to stay 4150 for now but ya, your right dominator probably would skip me over one of those stepping stones!

I went from a 48 mm TB, to a 52, to a 58, and now I am changing it all again. Should have went right to the big one, and saved some $$$.

i went from 2.29 gears to 3.23 just installed and no difference off the line not even a chirp!!!i have a 305 ho .30 ovr pistons holley 650 edle mani big cam th350 tranny ! my buddy's iroc same engine screeches off the line whats holding me back

How big is the cam?
You need heads, intake and headers for cam.............and a converter for sure.