Message-ID: <363F3B00.3994@erols.com>
Date: Tue, 03 Nov 1998 12:18:56 -0500
From: "Jeffrey B. Chipetine" <abcrental@erols.com>
Reply-To: abcrental@erols.com
To: lancair.list@olsusa.com
CC: abcrental@erols.com
Subject: OIL BLOWBY
Mime-Version: 1.0

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Dan Dudley's inquiry about oil blowby in Lycoming 320's is not uncommon
as any Cessna 172 lowly (low-life?)spam-can owner (like me!)can attest.
The Cessna Pilot's Association's John Frank has an informative artical
on this problem on the CPA Website, unfortunately, it is on the "Members
Only" side.  CPA email address is info@cessna.org  This is one of the
neatest groups I've come into contact with.  Very much like this group, 
they have an esprit c'corps and share information freely for the common
good. Possibilities on oil discharge 1) too much oil...when overfilled, 
1st qt will blow out within 30 minutes ( article comments that the
higher sump capacity may be to account for the longest range tanks
forseen as used by the assorted aircraft onto which the engine may be
affixed.  Good notes there on how to go about establishing a STABILIZED
oil level.  I would really reccomend that you inquire of the C.P.A. for
a reprint as it is valuable and I don't want a copyright suit on my
hands. 2) Cyl walls pitted or worn at mid cylinder. (borescope to
check).  3) piston rings stuck or misalligned. 4) leaking front
crankcase seal(they harden over time and fold back..not readily visable)
allows crancase to pressurize and oil blows out breather. 5) BREATHER
LINE OUTPUT LOCATED IN LOW PRESSURE ZONE ON AIRCRAFT CAUSING A SUCTION
TO BE CAUSED (common on the Cessna 201,  homebuilts on a case by case
basis)  6) if wet vac pump installed, a clogged oil return line will
cause air/oil seperator to vent through the breather.   Note:  while the
oil capacity of my C-172 w Lyc 320 is 8 qts,  it blows out till I get to
6 1/2 then stabilizes at about 1qt/10 hrs.  Much cheaper not to overfill
and throw the oil out the breather and very nice not to be cleaning the
belly of the plane once a week!.  regards to all.  Build Safe.. Jeffrey
B. Chipetine