Originally Posted by Brabs_Weather
My buddy put a oil separator from the valve cover to intake air line and had not one drop of oil. It is possible oil vapors are far less. The main area is from the crankcase behind the manifold. James Baron Racing has detailed pictures of this.
I said the main source is from the PCV system. The valve cover breather is just extra insurance. And I did find oil film in he tube that connected it to the air inlet tube.
This is common practice in the Mustang, Lightning, etc. world for instance. No catch can is really needed there unless you have a lot of blow-by.
Now between the PCV valve and the intake, that is another story. A oil separator/catch can is a must.
Btw, if you engine is in good condition, your can won't collect a lot of oil in a short period of time. If it does, then you have problems. If you can empty it at oil change time and get maybe a table spoon or two, then you are fine. Hopefully less.
F/I engines usually collect more than N/A engines for obvious reasons.