As the throttle opens, all the downdraft carburetors I've worked with make a transition from an idle fuel circuit to a main fuel circuit. When it is on the idle circuit, there is no visible fuel discharge above the throttle plates, but as the throttle is opened further, fuel starts to come out of the main nozzles.

I am wondering: for a given carburetor and engine, is float level the only variable controlling at what point fuel begins to discharge from the main nozzles?



1954 Crestline Victoria 312 4-bbl, 3-speed overdrive