valve cl to the head mating surface is what, about 5.5"-6", so that's a 10" runner length roughly. That assumes mathematically a constant cross section (as though the runeer were cylindrical or rectangular volume) which really isn't attainable (in most engine configurations) and doesn't compensate for taper and also doesn't consider compression, valve timing or many other variables...it also perobably assumes the rest of the engine is also going to be tuned for that peak as well (with no regard to making more power above that peak).
Taper variables can be huge, ex my 414 is about 3.87 sq inches (~3.2 x 1.2) at the plenum of the Victor intake, the head port entry is ~2.47" (~2.19 x 1.13") but immediately necks down at the pushrod pinch and the overall runner length is approx 10" (varies).
These are helpful in terms of getting optimum VE for a narrow operating range (EG the long ram mopar manifold from the 60's were designed primarily to boost acceleration in the "passing gear" range.
Is there a calculator for optimum runner length for peak power? I suspect you will find those runners much shorter.
A "better" way to look at it might be to take known runner lengths and cross sections and see where the optimum peak torque "naturally" occurs for a given displacement.
there is a direct correlation between cross section and "ideal" runner size for a given displacement.
The thing to Take away when dealing with standard port 440 big block engines is that the cross section is optimized for a much lower Peak torque RPM than what is typically desireable for a "high HP/cube" motor, as I've said the ports are barely 12% larger than a 340 which displaces 25% less size. to raise HP above the 'natura;l' torque peak you need more compression, more cam (when combined they are a way to overcompensate for the smallish port) and by keeping the runner shorter and as unrestricted as possible.
a tunnel ram does have longer ports, but don't forget they are also STRAIGHTER ports and are charged with a much larger Plenum area and (when carbs are properly sized) proportionally less pressure drop at WOT than a four barrel.
Reducing pressure drop across the venturi (getting as close to 0 as possible) improves torque output.
