[Chevelle-List] Valve Cover Breather

[Tom Tomlinson]

I'm replacing the intake manifold on my 350 Malibu. The oil filler tube is in the old manifold, but there is no provision for a filler tube in the new manifold, so I figure I'll move it to the valve cover. In shopping for a oil filler cap, I noticed valve cover breathers are available as well. This is probably a novice question, but what is a valve cover breather for, and what advantage/disadvantage would it have over a cap?   Tom Tomlinson