Is a Holley 650 Double Pumper Carb too big for a Ford 302 H.O. motor?
A 650 Holley, particularly a worthless double pumper is way too big for a tiny 302 with standard ring an pinion gears. 302 Fords also got into trouble with their large intake ports which were too big to keep the velocity up. When you paste on a "what ever" Edlebrock intake it'll bog like you were dragging 500 lbs behind you. You have no cam and cylinder-heads with ports that are too big. Forget fuel economy cause you won't have any.
It's going to bog without a lot of expensive modifications by a noted carburetor specialist. You'd be much better off with vacuum secondary 600 cfm. Holley. Intake velocity is the name of the game on the street for good throttle response.
What if I told you a 360 inch Chevrolet with dart platinum heads, any flat tappet cam, any intake and a *Holley 500 cfm two barrel would make 540 hp. @ 7,300 RPM.?
Why would you think you need a bigger carburetor on a smaller motor with 315 less horsepower? The trans-am 302 Mustangs had some success on the road courses where rpm could be hept up high but zero stock class wins in drag racing.