Dave:

Look back at my picture in post #8.

The "Standard" port crank requires one dtrilling, no precision, and one pass with an end mill or fly cutter. Angle and depth have to be right, but that's simple jigging. Fast and inexpensive.

To make the "Flowed" port a thrid cut is necessary, this time the same jig can be used, but now we have precise centering, exact depth of plunge, then a careful horizontal movement to locate the forward end of the cut.

This thrid cut will approximately double the machining expense and time needed for each crank. An easy place to cut production cost.

Bill.