<VV> PCV system on the Corvair

[moonpie8n at comcast.net]

There is always vacuum when the butterflys are closed [if the engine is running]. IN fact we used to set ignition timing [in the "OLD DAYS"] with a vacuum gauge. Just plug in the gauge, start the engine, and move the distributor slowly until max vacuum is achieved. I still use this method sometimes to get a starting point... 
Bob Isaac 
Moonpie Racing 
----- Original Message ----- 
From: Sethracer at aol.com 
To: lechevrier at earthlink.net, virtualvairs at corvair.org 
Sent: Thursday, December 16, 2010 3:03:00 PM 
Subject: <VV> PCV system on the Corvair 



In a message dated 12/16/2010 10:41:26 A.M. Pacific Standard Time, 
lechevrier at earthlink.net writes: 

>The 0.060" hole gives lots of vacuum / draw!! BUT.... The 1/2' tube 
to the filter housing is where fresh air gets in when the engine is not 
running....and where EXCESS blowby escapes 
> 

Those of your that want to hold to the company line, be my guests -- 
I'm not among this group. Read anything on positive ventilation of the 
crankcase, and it's benefits to the modern motor, and then note 
definitions for "positive flow ventilation" ... 



On the off-chance that we can call a Corvair motor a "Modern" motor <grin> 
- I believe there are two distinct crankcase ventilation modes to the (PCV 
equipped) Corvair engine - I guess a third mode is "not running". When the 
engine is running in good condition and little combustion byproducts are 
entering 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, in 
essence sucking the fumes back in under the carbs and into the combustion 
process. If the crankcase fume output exceeds the capacity of that little 
orifice - or it gets plugged up - the fumes travel up the tube into the inside of 
the factory air cleaner - where they also get pulled into engine for 
combustion. It would be interesting to place an extremely sensitive vacuum gauge 
on, say, the oil filler cap, and see if there is any vacuum pulled at 
idle. It wouldn't be much, but maybe it doesn't have to be much to do it's job. 
Except for the tendency for the feeder tubes around the fan to get plugged 
up with carbon, it is a pretty decent system. I make sure they are working 
okay on my cars. The system, unless it gets completely plugged, should 
always keep pressures from building up and causing oil leaks. 


Seth Emerson 

C's the Day! - Corvair, Camaro, Corvette 
San Jose, CA 



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