If you have the early 230Sl dip stick with the filter, then it's possible for excess crank case pressure to be vented through the tube. Later engines won't have this filter on the dip stick and all venting is done through the line on top of the valve cover.
Early 230 engines have a smaller port on the throttle body than the later engines probably because all crank case venting is routed through this system. Since the throttle valve is closed at idle, any real pressure build up won't be drawn away quickly enough and you may find that oil is being forced out through seals or cracks in gaskets. If you have that much blow by, it could be pointing to a bigger problem.