Panic,
The twin plugs were not the improvement, airplanes had twin plugs (and magnetos) almost from the beginning and my friends 1920's LaFrance firetruck has them, h*ll, even my 1998 Ranger. The improvement was supposed to be in air flow which was up some but not enough to justify the money spent. We often make several different port/chamber/runner/angle designs in the same head to test on the flow bench especially if we have an already botched head available. Otherwise just a single cylinder is made out of a 6 inch aluminum cube to flow test.
