Now, if the engine is idling and pulling say 20" Hg (Mercury)/about 10psi of 'vacuum', There should be about 4.7 psi of actual pressure inside the inlet manifold. If the crankcase is at about atmospheric pressure of 14.7psi, then there is a pressure differance of 9-10psi when the engine is idling.
Off throttle at high revs it will probably have an even bigger pressure differential.
So if the crankcase ventilation system was attached to the inlet manifold (as a lot of cars are) and engine 'vacuum' was used to help evacuate the crankcase gasses, it should also help prolong valve stem seal life because there should be much less pressure differential between the inlet manifold and the inside of the engine.
So not only should the valve stem seals last longer, there should be less tendancy for oil to be drawn past the seals even when they are starting to be less efective.
Thoughts and opinions?
