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1. 08:50 AM - Re: Oil in sump (Monty Barrett Sr)
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It is common for some oil to be in the plenum. The sump itself is full
of oil so I suspect you are referring to the plenum, which is part of
the induction system and is below the sump.
The reason that there is some oil in there is because when the engine is
operated at slow speed, such as taxi speed, the rocker boxes get
overfilled with oil, more so on a fresh engine where the ball sockets of
the pushrods have not bedded themselves to each corresponding rocker.
Then when the engine shuts down the oil in the rocker box will run thru
the intake guide, down the inlet pipe to the plenum, assisted by some
fuel which, when shutdown, will " dribble " out of the fuel nozzle,
diluting the oil and lowering is viscosity. Then the fuel evaporates
leaving the oil residue.
There are 1/8 NPTF holes in the lower edge of the plenum in which a "
sniffle valve " should be installed. Put a sniffle valve in the lower
port when the aircraft is sitting on the ground. This valve is used to
drain off residual fuel and oil. It's primary purpose is to minimize an
induction fire during a balked start. Use the one made by Airflow
Performance which has 1/8 NPTM thread on one end and -4 flare on the
other. Run a line overboard from underneath the cowling.
Monty Barrett
Barrett Precision Engines, Inc.
-----Original Message-----
From: owner-engines-list-server@matronics.com
[mailto:owner-engines-list-server@matronics.com] On Behalf Of
Speedy11@aol.com
Sent: Monday, April 19, 2010 4:09 PM
To: engines-list@matronics.com
Subject: Engines-List: Oil in sump
Engine Experts,
I have a Barrett IO-390.
When I removed one of the intake pipes from the sump to the
cylinder the other day, the sump had oil in it.
Should the sump where the intake pipes insert have oil in it??
If so, how much is permissible?
Stan Sutterfield
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