Oil catch cans arent needed unless youre running some type of forced induction.
It basically catches oil vapors that are running from the valve cover; which is called blow by. It prevents them from gunking up intake manifold. Also prevents a little oil burn off. (smoke)
As I said, theyre normally used for cars with forced induction. The pressure from whatever FI's being used causes oil to be forced out into the intake pipe and intake manifold.
Catch cans eliminate that.
My dads truck actually has a pump sucking pressure from his motor. Its some OEM Ford pump that runs 15in of vac at all times. It relieves pressure off the bottom end.
Its got a 383, fully built with a ProCharger kit. It moves
Heres a pic of my Mx-6's engine bay. I have a Jazz catch can. Notice off my valve cover theres 2 black hoses running to my firewall?
You cant see the catch can but its in the far left corner of my engine bay, by the firewall.