Quote Originally Posted by chevy 37
Bill my engine is a bored 305 to 315 with a fairy aggressive cam, with headers, dual plane intake and was running a 600 cfm carb which shows it being a little to big for my engine, but I've run a 650 before with no hesitation at all thru out the rpm range so I know the engine is OK with the larger carb. It's rated at 303 HP and 313 lbs. Used mostley for street driving but I hit the strip 3 or 4 times each year. I'm running stock heads that have been ported but will be changing to better flowing ones this summer.
If we use this formula
CID x MAX. RPM. DIVIDE BY 3456
With 315 Cubes and 6,000 rpms this works out to be 546 CFM.
This is based off 100% VE a good street engine would be at say 85% and this number then would be 464 CFM.
I rounded up to the next size which would be the 525 CFM Demon carb.