So I guess that's the real question; does a PCV system ventilate the crankcase any better than a pair of breathers on the valve covers?
Thanks for all the info so far.
yes a PCV does a better job then a pair of breathers. The breathers are mearly vents. The PCV actually pulls air through the system. As the engine burns it produces a little more then a gallon of water for every gallon of gas burned. There will be some leakage past the rings. So water vapor forms inside the crankcase. Normally engine temp will promote evaporation of the water from the oil and the PCV will draw that vapor out and replace it with fresh air. Without the PCV the water vapor (steam) doesn't flow out and condenses into the oil when the engine cools off.
Year ago, before PCV, engines had a breather and a road draft tube. the road draft fube created a mild low pressure area to draw away the vapors like the PCV. The only engines that run just breathers are race engines, but they get frequent oil changes/rebuilds.
Another benifit of a PCV is increased fuel economy. Some of those blowby gasses have unburned fuel in them. Mix that in with the air/fuel already going into the intake and it has a second chance at finding a spark plug to give it life.
Shy of an all out race engine, there is no reason not to use a PCV valve.
