<VV> PVC Blockage? -- PCV !!

[jay m]

ok, I don't know the details of Corvair's factory crankcase  ventilation 
setup - but look:
A standard PCV valve has a spring-loaded restrictor, to limit flow at 
high manifold vacuum and allow greater flow at low manifold 
vacuum/higher engine load.
As far as I know, a piston engine will have more blowby at higher load 
than at lower loads, and probably (at similar load)  more at higher 
speeds than low speeds.

AFIK, stock installations provide a passage between the air cleaner and 
the crankcase for two reasons:
1:  When the PCV flows more than the blowby being generated, you get 
fresh air into the crankcase.
2:  when there's more blowby than the PCV valve will flow, the excess 
goes into the air cleaner and the crankcase doesn't get pressurized. 
(well, more than permitted by the passage into the air cleaner)

The crankcase connection may go to the dirty or clean side of the air 
cleaner - some installations would have a little mesh or foam pad in the 
air cleaner (dirty side of the air cleaner element)  to keep the big 
stuff out of the breather tube.

Seems to me any motor with only a PCV valve and no vent hose would be 
very likely to pressurize the crankcase and leak everywhere.

Note that once the crankcase starts to pressurize, the PCV valve would 
see a higher pressure differential and might shuttle to its restricted 
position, making a bad situation even oilier.

cheers
Jay


On 4/13/2013 8:25 PM, Mark Durham wrote:
> My understanding of the positive crankcase ventilation system is it was
> the first step in emissions systems, and was a retrofit to the earlier
> corvairs. My original draft tube car worked just fine, however, it does
> pollute the air, whereas the current Corvair has a PVC on it which
> sucks out the gases, routes them to the intake where they will be
> burned. The little hose provides a pressure to the other side of the
> PVC to shut it off at higher engine speeds when it is needed less.
> Mark Durham
>


-- 
Jay