<VV> blow-by

corvairduval at cox.net corvairduval at cox.net
Tue Oct 28 19:04:16 EDT 2008


Your definition is correct. But blow-By can also get from the cylinder to
the crankcase by worn valve guides, etc, not just by the rings. 

What your symptoms describe is also blow-by.

The PCV system is designed for a small amount of blow-by. You have exceeded
its capacity. BTW, it is early 60s for PCV, not 50s, even in California. 

5000 miles on a rebuild should be at the best it will ever be, not still
seating rings. 

I suspect a bad rebuild job by the former owner, and it will never get
better. Old time remedies are to pour Bon-Ami scouring powder down the carb
while running the engine to scuff the cylinder walls. I would rather bite
the bullet and tear the cylinders off, hone them, measure them, and wash
with soapy water before reinstalling. New rings also, as the PO could have
easily broken one. 

OR, the PO could have put the rings in upside down. Some brands make a BIG
difference when the directions are followed! gggg  Other brands go in
either way.

You wouldn't believe how some people do a re-ring job, much less a rebuild.
All sorts of simple errors are committed.

Frank DuVal

Original Message:
-----------------
From: Ernie Sanders epssax at yahoo.com
Date: Tue, 28 Oct 2008 15:36:49 -0700 (PDT)
To: VirtualVairs at corvair.org
Subject: Re: <VV> blow-by


I thought blow-by was the gases that get by the rings on the compression
stroke and end up in the crankcase.  Old cars used to have a 'road tube' to
vent it out.  Around the 50's they started to route it back into the carb
to mix it into the intake and re-burn it.  After a short time they put a
PCV valve on it so a backfire couldn't have a direct route into the
crankcase and ignite the gases in the crankcase.  Ernie

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