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Old 01-11-2020, 09:28 AM
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dromuald dromuald is offline
Join Date: Aug 2012
Location: Newnan, GA
Posts: 32
Default sniffle valve required?

I have an RV 8 with an IO-360 injected motor. I bought the plane from the builder 7 years ago. At my recent condition inspection it was suggested that I install a sniffle valve on the bottom of the intake sump. That port is currently capped off with an AN fitting. This motor has 850 trouble free hours on it over the course of 17 years. My question is this - have I been lucky operating this motor or is the valve not really required. I realize it is used to drain the sump of residual fuel and or oil. If there is no drain does this fuel just get scavenged back into the intake system? I guess my point is why should I mess with success?
Dave Romuald (FFC)
RV-8 655CL
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Old 01-11-2020, 10:12 AM
Bavafa Bavafa is offline
Join Date: Oct 2007
Location: Sacramento, CA
Posts: 3,095

It is not required but it does help very much and it is a great addition for how little they cost or the ease of installation.
It helps drain the excess fuel in the sump when the engine is not running.
N825SM RV7A - IO360M1B - SOLD
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Old 01-11-2020, 10:14 AM
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bjdecker bjdecker is offline
Join Date: Jun 2005
Location: Georgetown, TX
Posts: 168

It would be interesting to measure how much residual fuel, oil, stuff, has accumulated in that sump after all these years...
Brian Decker
Retired Firmware Guy and Airplane Builder

2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned, Resurrected and flying
1998 RV-8 QB -- Started, Sold
1986 Mooney 205SE
1980 Mooney 231

Aided and abetted building a number of other RV's.
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Old 01-11-2020, 10:28 AM
BillL BillL is offline
Join Date: Sep 2007
Location: Central IL
Posts: 5,197

Originally Posted by bjdecker View Post
It would be interesting to measure how much residual fuel, oil, stuff, has accumulated in that sump after all these years...
Yep, next oil change when the engine is hot, take out that plug. If you feel lucky, don't put a pan under it. Mine drips sometimes, especially if flown rich and doing approach practices.

DanH does not have one either . . .

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Old 01-11-2020, 10:52 AM
vic syracuse vic syracuse is offline
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Join Date: May 2005
Location: Locust Grove, GA
Posts: 2,532

I've done inspections on those without them. Some nasty stuff comes out of that drain when the plug is pulled. It's a combinations of fuel and oil that drains back through the intake tubes when the engine is shut down.

Vic Syracuse

Built RV-4, RV-6, 2-RV-10's, RV-7A, RV-8, Prescott Pusher, Kitfox Model II, Kitfox Speedster, Kitfox 7 Super Sport, Just Superstol, DAR, A&P/IA, EAA Tech Counselor/Flight Advisor, CFII-ASMEL/ASES
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Old 01-11-2020, 03:21 PM
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JonJay JonJay is offline
Join Date: Jan 2007
Location: Battleground
Posts: 4,283

Probably should note to casual readers that a sniffle valve is for horizontal injection, not vertical.
Smart People do Stupid things all the time. I know, I've seen me do'em.

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Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
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Old 01-26-2020, 08:53 PM
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rswalden rswalden is offline
Join Date: Mar 2005
Posts: 99

Hi, Torque....
I installed mine when the engine was new and haven't had any issues. Easy, cheap installation that takes less time than reading through this thread. Just do it!
Bob Walden (Waldo), CFII-ASMEL
KFFC "Falcon RV Squadron" Peachtree City, GA
RV-7A Tip-Up, IO-390, 600+ Hours
RV-12 (Sold)... RV-12 Transition Training
EAA/AOPA/Vans Air Force 2020 Supporter
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