definitely a performance part that would be healthier on the bigger A series than the smaller ones in stock form. I found the oval port engines breathe quite well but restricted in this area with a stock manifold and carb compared to the A12 or smaller than A14 engines. About 20 years ago I witnessed a simple piece of square tube plenum bolted up to a set of Su oval port manifolds and a 28/36 weber on a stock A15 sunny engine and it definitely seemed way more responsive than the same carbie on the stock oval port mani with adaptor plate. There are many factors but that hillbilly larger volume setup didnt lose any torque at low speeds either.

Ive always been after a set of twin SU manifolds alone to recreate the hillbilly square tube plenum for a turbo setup but SU manifolds are very pricey these days unless I can possible source them from the states or some generous ratsun member.