wow.

It is NOT a one way valve. is it a HOLE. Nothing more. Sometimes the engine needs to inhale air, sometimes it needs to expell air. This is a relief port. SIMPLE. It is common practice to plumb 2 or 3 extra ports into the valve cover, with baffles, to improve engine health and breathing.

Plumbing the port into the intake arm will allow the engine to 'evacuate' and scavange oil vapours. It is the ideal setup. Some people plumb this port into there exhaust in other configurations...

Leaving this valve venting to the atmosphere will increase crank case pressures, cause a little more stess on the rings, but ultimately, as long as it can vent, it will not cause any noticeable to msot mild setups. maybe in 100km's it might induce ring wear, but nothing more.

Ben; Citing wikipedia. :thumbsdown:

Once again, this is not a PVC valve.