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.