I'm going to be swapping out my v6 for a 327 with 062 vortec heads and a GMPP vortec intake. I want to build the engine with everythign setup so that I can put a blowthrough setup (probably a centrifugal supercharger) later on. Because of that I want to use a holley double pumper so I can modify it down the road to make it compatible with the blow thru setup. Should I get a 650 or 750? How do I size the carb for the engine keeping in mind I will be putting a power addder on later? That might not be for a while so i want to make sure the carb isn't too big for the N/A setup but don't want to have to upgrade when I put the sc on. I'm thinking the engine should make about 300-350hp N/A and then 500-600 with the SC.

 

I would assume 750 would be fine until you get your upgrades. I'm not a mechanic though, so don't take my opinion. My engine pushes out 375hp and I have a 650 cfm carb. You might have some issues with a 750 until you get your upgrades but it will still run.

 

650.

 

So a 650 would be big enough even with the procharger?

 

Carb CFM = (C.I.D. x Max RPM) / 3456

Multiply your CFM by the Volumetric Efficiency your engine is capable of. For power adders usually 110%.

 

I forgot I have a good quadrajet that is currently a spare for my dirt track car. Maybe I'll just go with a quadrajet before the blower and then go for a 750 holley afterwards. Doing the math with the equation:
Carb CFM = [(C.I.D. x Max RPM) / 3456] * VE

Using:
VE = 110% with the blower
Max RPM = 7000

Gives me 728cfm.