I recently purchased a Rochester 4GC that was rebuilt. I installed it on a 300ci 64' Special with a stock 300 4bbl intake. The mixture is extremely rich. It is fouling out the plugs after about two or three days drive time. The idle mixture screws have no effect on this. Should i adjust the floats to be lower or higher? or, should I get new jets of a smaller diameter? Or, could it be the accelerator pump? All suggestions will be helpful. I'm dying to drive my buick this summer. Thanks, Mike
Though I am not sure of the metering devices on this carb, metering is basically of two types; The first, is with the use of metering rods in jets, controlled be engine vacuum. As vacuum drops, the spring controlling the power piston pushes the metering rods out of the jets, enriching the mixtures. On the other type, similar to Holleys, uses a power valve which opens the extra fuel passages under power, thereby enriching the mixtures. It is possible that eithger the power valve ois damaged, allowing power mixtures at all times, or that the power piston is stuck in the up position, or that the metering rods are missing, allowing the carb to free flow fuel into the engine. You might try lowering the float level, but unless the carb is flooding, I suspect a mistake was made regarding the metering components. It is also possible that the incorrect carb was selected by the rebuilder. Ray
