Just bought a '64 falcon wagon. Its got 2 600 AFB carbs on an offy intake. While it does have a pretty stout solid lifter cam Im thinking 1200 cfm still pretty overkill for a 302. Id like to pick up 2 450s or maybe even 390s. Does anybody know what kind of carbs will fit an offy? Id like to get a couple holleys but they might be too long to clear each other.
Carb sizing depends on manifold design. If your have a dual plane 180 degree manifold, for the purposes of carb sizing, your engine sees that 1200 CFM as 600CFM. Still too much, but not as bad. If you have a single plane "360" degree Offy manifold, the engine is pretty much seeing all 1200 CFM. But beyond that, if you do have a single plane Offy "360" intake, I wouldn't use it al all. Although that manifold was a performance improvement over the stock manifolds being used when it was designed, at this point there are much better manifolds available for your engine.
Why mess with it if it's working ? I run two Carter 600's on my 355 mild motor and it loves it, they work off vacuum so only give you the cfm that you need anyhow.
It is customary to install Holley carbs with the float bowls fore and aft. If you want to switch to Holleys it's not a problem to run them with the carb(s) rotated 90 degrees, which puts the float bowl(s) at the sides. For reasons I don't understand, over the years some successful racers have chosen to run single 4-barrel carbs "sideways". Of course, different throttle linkage will need to be needed to make your 2x4s work that way.
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