You made a catch can? Can u show pics and possible items used to make it?There is a PCV valve in the head cover; as member ronnie has pointed out, the large 3 manufacturers got a PCV valve "certified" to use as a crankcase ventilation system a long time ago. It allows the gases from ring blowby to venilate through this valve, and back into the intake to be reburned. It also allows oil mist, which over time, can get onto the backsides of the valves, causing poor performance. I never thought much about this until I made a catch can. I now empty about a teaspoon of oil out of it every 3 to 4 weeks.
PCV Looks like this: