Jason4x4
1/2 ton status
http://www.aa1car.com/library/pcv.htm
open or closed is strictly a emissions deal.
The Positive Crankcase Ventilation (PCV) system reduces blowby emissions from the engine. About 20% of the total hydrocarbon (HC) emissions produced by a vehicle are blowby emissions from gases that get past the piston rings and enter the crankcase. The higher the mileage on the engine and the greater the wear on the piston rings and cylinders, the greater the blowby into the crankcase.
Before PCV was invented, blowby vapors were simply vented to the atmosphere through a "road draft tube" that ran from a vent hole in a valve cover or valley cover down toward the ground.
In 1961, the first PCV systems appeared on [COLOR=blue ! important][COLOR=blue ! important]California [COLOR=blue ! important]cars[/COLOR][/COLOR][/COLOR]. The PCV system used intake vacuum to siphon blowby vapors back into the [COLOR=blue ! important][COLOR=blue ! important]intake [COLOR=blue ! important]manifold[/COLOR][/COLOR][/COLOR]. This allowed the HC to be re-burned and eliminated blowby vapors as a source of pollution.
The system proved to be so effective that "open" PCV systems were added to most cars nationwide in 1963. An open PCV system draws air in through a mesh filter inside the oil [COLOR=blue ! important][COLOR=blue ! important]filler [COLOR=blue ! important]cap[/COLOR][/COLOR][/COLOR] or a breather on a valve cover. The flow of fresh air through the crankcase helped pull moisture out of the oil to extended oil life and reduce sludge. The only drawback to these early open PCV systems was that blowby vapors could still backup at high engine speed and loads, and escape into the atmosphere through the oil filler cap or valve cover breather.
In 1968, "closed" PCV systems were added to most cars. The breather inlet was relocated inside the air cleaner housing so if pressure backed up it would overflow into the air cleaner and be sucked down the carburetor. No vapors would escape into the atmosphere.
open or closed is strictly a emissions deal.
The Positive Crankcase Ventilation (PCV) system reduces blowby emissions from the engine. About 20% of the total hydrocarbon (HC) emissions produced by a vehicle are blowby emissions from gases that get past the piston rings and enter the crankcase. The higher the mileage on the engine and the greater the wear on the piston rings and cylinders, the greater the blowby into the crankcase.
Before PCV was invented, blowby vapors were simply vented to the atmosphere through a "road draft tube" that ran from a vent hole in a valve cover or valley cover down toward the ground.
In 1961, the first PCV systems appeared on [COLOR=blue ! important][COLOR=blue ! important]California [COLOR=blue ! important]cars[/COLOR][/COLOR][/COLOR]. The PCV system used intake vacuum to siphon blowby vapors back into the [COLOR=blue ! important][COLOR=blue ! important]intake [COLOR=blue ! important]manifold[/COLOR][/COLOR][/COLOR]. This allowed the HC to be re-burned and eliminated blowby vapors as a source of pollution.
The system proved to be so effective that "open" PCV systems were added to most cars nationwide in 1963. An open PCV system draws air in through a mesh filter inside the oil [COLOR=blue ! important][COLOR=blue ! important]filler [COLOR=blue ! important]cap[/COLOR][/COLOR][/COLOR] or a breather on a valve cover. The flow of fresh air through the crankcase helped pull moisture out of the oil to extended oil life and reduce sludge. The only drawback to these early open PCV systems was that blowby vapors could still backup at high engine speed and loads, and escape into the atmosphere through the oil filler cap or valve cover breather.
In 1968, "closed" PCV systems were added to most cars. The breather inlet was relocated inside the air cleaner housing so if pressure backed up it would overflow into the air cleaner and be sucked down the carburetor. No vapors would escape into the atmosphere.

I guess I was wrong, all hail 4x4high!!


Keep in mind that a clean filter wil cause little, if any, restriction anyway. My smogger stuff has the hose to the filter housing, and my exempt stuff doesn't. That way the air filter lasts longer on the old ones by not getting oily.