What would be the best carburetor and jet set up for a 509ci about 550hp with 9.1 afr heads with 741 cam. Cmi headers..
Looking at buying a brand new holley. Also looking at the ultra xp carbs, since I have a dominator intake on the motor. And would rather not have to change the intake . What cfm would be the best? 850?

750-800 would be fine, the quick fuel are great carbs

since you already have a dominator intake i would go with a 1050 2 circuit carb.i like the quickfuel carbs but plenty of brands to choose from.some are going to say that 1050 is to big but my experiance sais otherwise.

Would an Hp 500 carb be perfect for this setup?

Not perfect but would work well. Probably easiest to tune since it was 'factory' tuned to a little lesser of a motor.

An 850-950 (or HP1000) would be right on the money. If engine is machined, assembled and clearanced right, the OP should have between 575-600HP.

Don't see the need for a million dollar carb on this one, but that's my opinion.

that is where I am at on an iron headed 509 9.8:1 motor(lots of porting and an air gap intake, ultradyne cam. always wondered if a dominator would help or hurt. Holley 850 with the proform HP center body and billet butterfly assy, a 22hp gain over the stock holley dp with choke horn

Well, you have a dual plane, so you are effectively using less cfm out of your carb than a single plane intake would, so yeh, you could use a bigger carb.

Great low cost flowbench for a carburetor is a vacuum guage.

Sorry,[ATTACH=CONFIG]544423[/ATTACH] typing and getting 2 motors mixed up, running a ported Merlin single plane intake on the 509

most HP carb sites have a CFM rating for cu in vs RPM bet will come back close to 750

I'd suggest goint taller on your K&N. That's probably why removing the choke tower picked up some hp.