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Engines-List Digest: 1 Msgs - 04/20/10

 
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Speedy11(at)aol.com
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PostPosted: Wed Apr 21, 2010 12:24 pm    Post subject: Engines-List Digest: 1 Msgs - 04/20/10 Reply with quote

Monty,
Thanks for your response and your explanation - that was exactly the info I needed.
I was referring to the plenum, but another guy had called it the sump, so I called it that thinking my terminology was wrong.
The engine is running great - only a few minor hiccups. I have some surging during taxi. I'm not sure what is causing it, but I probably need to adjust the idle. And I have a minor, but aggravating, oil leak that we're tracing. Local A&P is going to wash the engine and I'll do multiple engine runs to try and local the leak.
I'll add the sniffle valve you mentioned.
Thanks,
Stan Sutterfield
[quote]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.

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rv8a2001(at)yahoo.com
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PostPosted: Wed Apr 21, 2010 1:32 pm    Post subject: Engines-List Digest: 1 Msgs - 04/20/10 Reply with quote

Surging at idle when hot is boiling of the fuel in the injector lines......at least for me. Very annoying in the summer time!

Scott
RV-8a



From: "Speedy11(at)aol.com" <Speedy11(at)aol.com>
To: engines-list(at)matronics.com
Sent: Wed, April 21, 2010 1:23:53 PM
Subject: Re: Engines-List Digest: 1 Msgs - 04/20/10

Monty,
Thanks for your response and your explanation - that was exactly the info I needed.
I was referring to the plenum, but another guy had called it the sump, so I called it that thinking my terminology was wrong.
The engine is running great - only a few minor hiccups. I have some surging during taxi. I'm not sure what is causing it, but I probably need to adjust the idle. And I have a minor, but aggravating, oil leak that we're tracing. Local A&P is going to wash the engine and I'll do multiple engine runs to try and local the leak.
I'll add the sniffle valve you mentioned.
Thanks,
Stan Sutterfield
[quote]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.

--


- The Matronics Engines-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?Engines-List
Back to top
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