So I have 4 sets of Carb intake manifolds. Long ones short ones and one inbetween. Also I noticed that one of the short ones had a 50mm opening at the top.
others had 48mm one is actually 47mm.

So why don't they make 40mm and 44mm openings keeping the runner ID smaller to increase velocity?

What kind of effect can I expect with different length intakes? 44 IDF's 500 lift 290 duration cam 2.0L heads stock size valves all port matched exiting out SSI Bursch exhaust.