We’ve got the answers—the Summit Racing tech department tackles your automotive-related conundrums. This week, we help choose the right carburetor for 1960s era Fairlane.
Q: I have a 1967 Ford Fairlane with a 289 small block. Upgrades include an Edelbrock intake and carburetor, MSD ignition, Hooker Super Competition headers, a 2 1/2-inch dual exhaust, and an Auburn Gear Pro Series limited slip differential with 3.55 gears. The engine internals are relatively stock except for a mild cam.
My question is about carburetor cfm.
I’m considering replacing my intake and carb with an Edelbrock Performer RPM Air Gap manifold and Demon carburetor. My current carb is 600 cfm, but I’m wondering if I would get more performance from a 525 cfm carb because of my engine’s smaller displacement. Would 535 cfm starve the engine of fuel at 5,500 rpm? Would the 625 cfm version be too large and leave my engine struggling at lower rpm? What do you recommend?
R.H.
A: Without knowing the exact specifications of the camshaft, it’s difficult to make a suggestion. The folks at Demon Carburetion do have guidelines for all of the their carburetors. For the 525 cfm Road Demon carbs, they recommend installation on 260-400 CID engines with a camshaft rated 210 degrees of duration or less at .050-inch lift. The 625 cfm Road Demon carbs should be used on 302-460 CID engines with up to 220 degrees of duration. We mention this because our carburetor recommendations are based on engine vacuum and rpm range. The camshaft has a lot to do with that.
We’d suggest you step up to the Road Demon 625 in this case because of the performance upgrades you’ve already installed. When properly tuned, the Demon 625 will provide your ride with great throttle response, power, and performance.
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