<VV> PVC system on the Corvair

kevin nash wrokit at hotmail.com
Sun Dec 19 13:23:26 EST 2010



> Message: 1
> Date: Thu, 16 Dec 2010 17:22:26 -0800
> From: Chris & Bill Strickland <lechevrier at earthlink.net>
> Subject: Re: <VV> PCV system on the Corvair
> To: VirtualVairs <virtualvairs at corvair.org>
> Message-ID: <4D0ABB52.60208 at earthlink.net>
> Content-Type: text/plain; charset=us-ascii; format=flowed
> 
> 
> > 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 
> suction.
> 
> 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

 Bill-I agree, there's no point in running a pvc system on a corvair if the oil cap and dipstick
are not properly sealed, as any "vacuum" is leaked, keeping the crankcase approximately at
atmospheric pressure. However, if a person were to go ahead and do the modifcations necessary
to seal the oil filler cap and dipstick, and install a well made pvc valve that vents to the air cleaner
and has a line attached to a vaccum source, those oil leaks will go away, and the engine may 
produce a bit more power, as there is a little less air sloshing around in the crankcase. It works
because there are slight pressure spikes produced in the crankcase, caused by all that air underneath
the pistons bouncing and sloshing around. If the pressure spikes are allowed to escape, and no air
is allowed back in, a slight vacuum is produced. This is the pvc valve I plan on running (when I get
to it!!)  http://www.et-performance.com/turbo.html
 
Kevin Nash 63 turbo, daily driver
 		 	   		  


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