Why is ther no formula to figure out port volume?

ramcharger said
Interesting about the small LCA's bringing smaller port heads to life. Could the increased overlap be facilitating the ram tuning effect of the smaller ports or do the smaller ports just need the additional overlap that a larger port doesn't need? If this is the case, that smaller ports just need the additional overlap that a larger port doesn't need, would you consider the larger ports more effieceint at higher rpm regardless of rated flow?

Small ports with high velocity work the best with large overlap cams, as if used with a large port head would have a flat spot or sag on the bottom end because of low or slow air speed in the port. As for the larger ports being more efficient at higher rpms, well all heads will become efficient at some point in the rpm range, but where is determined by the amount of engine under them and how well the engine was built.

Lets say I start with two identical heads. Just for fun, lets say they are W2's. One heads intake ports are hogged out to 210cc and the other is 195cc. Both flow 290 cfm @ .600" lift. I am using a cam with .610 lift at the valve, 260 degrees of duration @ .050" and a 110 lobe center on a stroker SB 408. Carb is a 850 cfm Holley double pumper derivative on a Mopar W2 single plane intake. Compression ratio is 11.5:1.

Will the 210cc head have more top end than the 195cc head? Would the dyno show identical numbers? Would the peaks (TQ and HP) be the same? Would the hogged out head have less TQ under the curve? Would the higher velocity of the small port head beat the large port head on all points?

The 210 and the 195 cc head should have about the same top end on a 408 as a engine that size won't need much more than 195 cc's so the larger head should ET and MPH similarly. As for the dyno showing the same numbers NO it won't happen, the smaller would show better TQ and maybe 10 HP less verses the large port head.