How important is it to have a breather on top of the catch can? What kind of problem can I expect without one? Just a closed system like them ones on Ebay for $4.99 and $20 shipping, there not vented. Can I just make the hole on the top myself and use a breather filter like the ones that fit the valve cover.

 

I don't see a breather ....

 

In a closed system, there will be no where for the pressure to go, and that is a bad thing. To run no filter, you need vacuum from some source like your intake tube or your exhaust to evacuate the pressue coming out of the motor into the catch can.

Either just make a can yourself and yes put a filter on top or you could buy one of the greddy one like dude posted a pic of and cut a hole and make a way for the filter to attach.

If emissions is a concern in your area, you will have to run it to the intake tube like the factory PCV system.

My catch can setup is two lines off the back of the block to a catchcan with a filter, and two more lines off the valve cover to another catchcan with filter.