<VV> PCV system on the Corvair

Chris & Bill Strickland lechevrier at earthlink.net
Thu Dec 16 20:22:26 EST 2010

>  The system, unless it gets completely plugged, should always keep 
> pressures from building up and causing oil leaks.

I fully agree, Seth, one does not want pressure building up. But with 
the good running engine with normal combustion bypass, in addition to  
sucking up such vapors, one wants to provide fresh air inlet to purge 
those crankcase vapors, including the water vapor portion of the 
combustion bypass -- without the "ventilation" part, that moisture can 
get trapped in the crankcase.

 > the orifice in the PCV tee is supplying main engine vacuum to the 
crankcase - well, a bit of it anyway, through the tee

Heh, heh -- not really.  It is more like holding a vacuum source out to 
the open atmosphere and thinking that it is sucking your crankcase -- no 
way!  (unless maybe your air cleaner(s) is(are) plugged -- the balance 
tube only will get what is forced out of the crankcase into the air 
cleaner tube, where it mixes with the air cleaner air.

 > It would be interesting to place an extremely sensitive vacuum gauge 
on, say, the oil filler cap,

That was one of the early PVC testers -- little round flat thing with a 
ball in it that was sucked up a ramp, when it worked. better than a 
gauge, you could set up a manometer tube, or the U-shaped version to 
compare vacuums here and there, but assuming the air cleaner has a good 
system, it should be at atmospheric pressure internally. Likewise, the 
air cleaner tube, meaning there is atmospheric pressure at the PVC / 
orifice -- please explain where the "crankcase suction" comes from ...   
however much your orifice or PVC sucks, it will still be at atmospheric 
pressure on the air cleaner side, and thus, so will the crankcase -- no 

And I think we all know what happens when you take the oil fill cap off 
a running stock Vair  -- it may as well be on an overhead cam valve cover.

Bill Strickland

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