How many CC's does it take to fill the port full of liquid? This gives you your port volume.
I agree that too much port volume will hurt the performance of the engine, and with the flow #'s that you posted they have to be fairly large. This is why we are asking.
This also is what they call over heading a engine, its where the heads are too large for the needs of the engine. Generally the result will be sluggish low end performance and loss of port velocity, also the engine won't rpm like is should so performance will be down from where it should be.
