Offenhauser Dual port ??

I very much remember the published reports on these back in the day, and the top end restrictions were very real. And flow disruptions stepping from the small primary ports to the heads ports when only on the primaries was suspected to be a flow disruptor at lower speeds. There just was no compelling reason to use this concept over other designs, even for economy use and torque, and it quickly died away.

Other manifolds performed better across all RPM ranges.