Re: New block
Scavenging helps draw in the intake charge before the exhaust valve closes so it's important that there is no interference in flow on either side of the equation. A divergent duct where flow it taking place, increases pressure and decreases velocity. It's all Bernoulli's principle. The opposite, a convergent duct, reduced pressure and increases velocity. The proposed port design diverges in the middle then converges toward the end so I don't know what that will do there. All I'm mentioning is that it might not allow enough scavenge effect as a duct that has no divergence or convergence to it. Someone that knows this stuff better than I should take a look at this.
The center port has a tendency to do the same thing so some folks put those dividers in there to decrease the effect but the way the firing order is, it doesn't seem to affect it except at higher flow rates or higher RPM. This might be part of the reason that flatheads drop off at around the 4000 to 5000 RPM range. The other part would just be the size of the ducts. Ford only made them so big in order to fit into the overall design.
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