<VV> PCV system on the Corvair

Sethracer at aol.com Sethracer at aol.com
Thu Dec 16 15:03:00 EST 2010

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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