Attached is a picture of an 2 barrel intake manifold that GMC made for their 302 engine with big port heads. The intake ports are bigger but the runners (I call it volume) is/are not that much bigger than the stock 230/250/292 manifold with a single barrel carburetor. Why didn't GMC have a manifold design like Clifford or Aussie?
For the intake design, there is a term of "precharge" and I take it that there is a critical point where the best and correct amount of vaporized fuel is desired to be available at an optimum timing of the cylinder piston position, intake and exhaust valve timing and engine RPM. Likewise there is an optimum of head exhaust port size, exhaust manifold port size and exhaust pipe diameter to get the optimum "scavenging" to help move the exhaust out faster.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
