MGA Crankcase Ventilation Test and Analysis

The function of the MGA crankcase ventilation system, is often described as follows; The open end of the draft tube near the oil pan, is cut at an angle (long side facing up wind) and the air moving under the vehicle flows across the opening while driving, creating a venturi effect, causing a vacuum in the tube. The vacuum draws fresh air into the rocker cover vent from the air filter, down and through engine cavities and crankcase, then out the draft tube. In doing so it removes the harmful blow-by gasses, keeping the crankcase and other internal cavities clean. But does it really?