ive been building my 347 for a while and ive got most of what i need to finish it but i dont know what size carb to run im running 9to1 comp, twisted wedge heads, air gap manifold, i dont care about gas mileage its not a daily driver what size should i run

 

foxmann347...........You could get a lot of variable opinions on this. There are many factors that should be considered, maybe the most important being your desire for good quality idle, fair fuel efficiency, and and good performance. The big carbs are impressive to look at on the engine, but may not give you want you really need.Advice I received long ago a good all around enginebuilder is to use this formula:

Cubic Displacement divided by @ (example: 347 divided by 2 = 173.5)
Maximun RPM divided by 1728 (example: 6000 RPM divided by 1728 = 3.47)
Multiply those two results numbers (example: 173.5 X 3.47 = 602 CFM)

To really get it right, you need to figure in the Volumetric Efficiency. Some shops could test that for you. A regular street car will run at somewhere close to 75%. Your heads and manifold could boost that a little, but let's use the 75% here. (example: 602 CFM X 75% = 451 CFM).

If it were mine, and using this formula result, I'd bump itup to 600 CFM. Those 750 or 850s double pumpers will disappoint you, in my opinion.

 

Meant to add that I would contact a couple of carb manufacturers, give them your engine and mods, how you will use the car, and get their opinions.