valve cover breather

[Aussie Challenger]

Dredging up an old topic because I came across it and I have always wondered ----

I can see that if you have closed valve covers, with no breathers at all, then you could have the issue you talk about....blowing out gaskets.

But if you have a breather on one or both rockers, effectively venting them to air, wouldnt that eliminate any possibility of blowing out gaskets due to pruessure building up?  Even without the carb sucking in fumes, the pressure would not rise as it would escape through the breathers....

 

From what I understood, PCV was mostly  an emissions change, keeping the vapors contained.

The old vent tube was very inefficient and blocked up after a while, but better than nothing, it was the fact that oil could be dropped on the road surface that prompted the introduction of the PCV system. Having oily fumes going back into an engine to be burnt is not ideal but works OK.
Race engines have tubes that go to a 'catch can' to over come dropping oil on the track surface.
Just having the mesh filled oil caps end up depositing oil on the R/C and around the engine, not a good look when we spend considerable amounts to dress up our power plants.

[Mopar Mitch]

Under high-rpms, for lengthy periods of time, such as HPDE/HSAX/AX and when the engine oil is very hot, I've experienced oil blow-by coming from the breather of the non-tube style.  So, I've added a lengthy hose routing around the back of the six-pack air-cleaner, to one of the drain-back lower tubes of the air-cleaner... grossly reduces the problem, although, oil is probably held inside that long hose.  Another thing I've done is added a catch can (vented plastic 1-qrt oil container) with the hose going into it.    I'm not comfortable with this setup and may try something different.... pcv valve seems ok, although the hose does seem to be a little squeezed/restricted.

Any comments?   T/Anks ahead!

PS:   synthetic oils (~20-50) tend to have more blow-by, in my experience, with the above described problem.

[Aussie Challenger]

Plastic is not a good item to use as a catch can, most racing bodies stipulate a specific container for this use. Some speedway's apart from a catch can have a drain back using the inertia of the oil collecting in the passenger side R/C wanting to go in one direction to then direct it back to the sump area. Not having a PCV system on a road car tends to fume also which end up annoying the driver and passengers.