A single plane manifold pulls from the carb plenum on the same level, all cylinders pulling from the same pot of air.
The dual plane manifolds, have 2 different levels that separate opposing cylinders, to keep them from drawing the fuel mix to 2 cylinders at the same time.
Dual plane intakes run nice on the lower rpm range, and work well for the low end torque. Better Drivability
Single plane intakes work well for high rpm engines.
