[Dwight Southerland]

Under uniform acceleration, the manifold could be made to be pretty efficient. When used in constantly changing engine speed conditions (on and off the gas like a road racer) they were hard to make work. The large plenum area made it necessary to have large accelerator pump shots to cover the volume of air in the plenum. That made for inconsistent A/F mixtures and thus inefficent power levels and performance. Also, since one of the ideas behind the design was to make uniform runner length, the effective power band tended to be narrower than on single plane manifolds with a variety of runner lengths.