<VV> Varying Compression Readings?

[N. Joseph Potts]

I've been checking compression for many years, and have developed certain
habits. While I follow these habits as consistently as I can, I can't say
they are "right."
     It's my THEORY that the "compression" of a cylinder "is" the MAXIMUM
that the cylinder can pump the gauge up to. The reality, if there even IS
one, is probably otherwise, but in this, consistency is more important than
absolute accuracy. That said, I COUNT the times I turn the engine over to
get any cylinder's compression. My number is six. Five might be just as good
(consistent), and seven, too. Two (which you used) obviously will give you
lower readings. Maybe THAT is better. It certainly drains the battery less
(and the battery draining is ONE of several things that can make your
first-tested cylinders read higher than your later-tested cylinders, and is
ONE of the reasons why sometimes I "go around again" just to try to level
things out across cylinders).
     Hope this hasn't deepened your confusion too much. At the end of the
day, I tend to be a bit philosophical about compression readings.

Joe Potts
Miami, Florida USA
1966 Corsa coupe 140hp 4-speed with A/C

-----Original Message-----
From: virtualvairs-bounces at corvair.org
[mailto:virtualvairs-bounces at corvair.org]On Behalf Of GYoungwolf at aol.com
Sent: Saturday, April 02, 2005 12:36 PM
To: virtualvairs at corvair.org
Cc: bruce_covert at yahoo.com
Subject: <VV> Varying Compression Readings?

I was checking compression on a '64 110 engine today, when I noticed that I
can "pump up" the readings. Am wondering what that means? I was using a
screw-in (sealed with an 0-ring) compression gauge. With a couple of revs,
the
readings on all cylinders were a fairly consistent 95-100. But, if I
continued to
crank the engine, the compression reading on several of them could be pumped
up
to 125+. What, if anything, could this mean? (Plugs are carboned up a bit,
but
nothing serious or wet.) Engine does not "smoke." Another out of sorts thing
I noticed was a very oily pcv pipe (PG trans) and some oil residue puddled
in
the "duckbill" in the top of the carbs. (Worn rings??). I'm not sure of the
mileage on the engine as the odo reads 12K, but that is almost clearly
neither
original or 112K.
Thanks,
Grant