Thread: Dual plane vs. Single plane

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It has to do with cylinder filling and mixture velocity. With a dual-plane manifold, each cylinder sees only half the volume in the manifold as opposed to a single-plane, where all the volume is seen by each cylinder as it ingests its load of mixture. It doesn't take as long for a cylinder to pull a vacuum in half the volume, so a "half-volume" dual plane works better at lower rpm's due to a faster mixture velocity and subsequent better signal to the venturi of the carb. When the mixture slows down, the carb has a tough time calibrating the fuel to air ratio that it is going to feed to the motor.

At higher rpm's, there is more air moving through the motor and using twice the volume of a single plane is not a problem.

Look through Edelbrock's offerings and pay attention to the rpm range for each individual manifold. Every manifold has a minimum and maximum operating range depending on what you are using the motor for.