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View Poll Results: sniffle valve yes or no?
Yes must have a sniffle valve 40 66.67%
sniffle valve is not really needed 20 33.33%
Voters: 60. You may not vote on this poll

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Old 02-12-2010, 11:50 AM
JoeBlank's Avatar
JoeBlank JoeBlank is offline
Join Date: Mar 2005
Location: Molalla, Oregon (KOL05)
Posts: 530
Default Precautionary components

Sniffle valves (like fuel filters and carb heat systems) are precautionary components in Firewall Forward systems and not absolutley required or necessary for the engine to operate. These systems are designed to prevent certain failure modes in the event that some out-of-sequence or non-standard event occurs. That event could be the result of fuel drainback into the sump or water ingestion from a few days parked on a rain soaked ramp. Both could ruin your engine and your day. Just think of it as another insurance policy.

A sniffle valve (Lyc P/N LW-75444) is only used on Horizontally Inducted, Fuel Injected engines on RV's, in which the Injection Servo is mounted to the forward face of the sump. A Vertical Inducted engines does not require one.
Joe Blank
Advanced Flight Systems

Van's Aircraft Inc. Technical Support-Retired
EAA Tech Counselor & Flight Advisor
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Old 02-12-2010, 12:56 PM
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hydroguy2 hydroguy2 is offline
Join Date: Sep 2006
Location: Townsend, Montana
Posts: 3,148

Here's a excerpt from an email I received from AFP:

With the correct use of the purge valve for starting and stopping the engine there should be no fuel getting into the sump. However in the event that proper procedure is not used, a manifold drain (sniffle valve) might be a good piece of insurance.

So seems the safest thing to do is put one on, but not absolutely necessary. I have elected to follow procedure, hangar my plane, don't fly in the rain and NOT install the valve. YMMV and I may grenade my motor.
It's just one Dam job after another
Brian, N155BKsold
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Old 02-12-2010, 04:01 PM
Jerry Cochran's Avatar
Jerry Cochran Jerry Cochran is offline
Join Date: Jan 2005
Location: Sherwood, Oregon
Posts: 978
Default Test that sniffle

Just make sure you test the sniffle valve. The first one I got from Superior leaked air when it was supposed to be closed. They said they'd never seen one do that before. Yah, right.

One might get erratic running if this thing decided to leak just occasionally...

Otherwise, might not be that much diff...

Anyhow, never had a problem with my trike but understand quite a few TD's did.
Jerry Cochran
Sherwood, Oregon

RV-7a 707DD Bot from David Domeier 12/01/11
Lycoming IO-360 Catto 3 blade Panel upgrade in progress

RV6a 18XP 1st flite 03/21/07 sold to Dale Walter 10/22/2011
Superior IO-360, Hartzell Blended, GRT/Dynon

Happily "autopaying" DR

"Suppose you were an idiot, and suppose you were a member of Congress; but I repeat myself."

Mark Twain
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Old 02-12-2010, 04:18 PM
shuttle's Avatar
shuttle shuttle is offline
Join Date: Dec 2006
Location: UK
Posts: 368
Default Right-Angle Sniffle Valve

Joe posted a part no. for a sniffle valve. I bought one of these from Van's.
However, with my TMX-IO-360-M1B this straight sniffle valve conflicted with my Vetterman's cross-over exhaust.

I solved it with a Piper right-angle sniffle valve - Piper P/No is 492-091.

Search VAF on this P/No and you'll see it quoted by Mahlon at Mattituck.

It's a shame that Van's don't offer the right-angle part.
Steve Hutt
West Sussex, UK
RV-7 G-HUTY (not flying yet)
( Tip-UP / TMX-IO-360-M1B / Hartzell 7497-2 / 1x LSE PLASMA III / Dual AF4500's / AF-Pilot AP / 695 )
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Old 02-13-2010, 08:26 AM
Don at Airflow Don at Airflow is offline
Join Date: Jun 2006
Posts: 316
Default 90 degree Manifold Drain

Or you can order P/N 1090138 Manifold Drain ($21.00) and P/N AH-3400X2 90 degree pipe fitting ($1.50). And there you have it all for $22.50.

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Old 02-13-2010, 10:16 AM
tomagin tomagin is offline
Join Date: Aug 2007
Location: Port Orange, Florida
Posts: 84

Similar to a previous post I had the "hydrolock" problem on my new Lyc with the Silverhawk injection. So much fuel accumulated during the "washout" process suggested by Lycoming to purge the preservative oil that the engine locked up. Was also lucky that it did not start and bend something!

After draining the cylinders and trying again I finally took the plug out of the hole the sniffle valve goes in and almost a quart of fuel came out. After that drain it started normally but I didn't start it again until I had the sniffle valve in place.

In my view the horizontal injection with the Silverhawk requires the sniffle valve but it was never so stated in any of the instructions and a sniffle valve is not part of the FWF kit from Vans.

BTW, I bought the onewith the 90 deg bend on the outlet that is used on the Piper Twin Comanche and it was easier to install. The one Vans sells is sort of blocked by the heat shield and Vetterman exhaust.
Tom Agin
Port Orange, FL
QB RV-8 completed!!
XIO-360-M1B with LASAR
GNS-430, GI-106A, GTX-330, 9000EX, Becker 4201, Digiflight II VSGV, ADI, Dynon Dlight Dek 180, Vertical Power VP-200
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Old 02-13-2010, 09:10 PM
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osxuser osxuser is offline
Join Date: Aug 2005
Location: Pasadena CA
Posts: 2,482

The reason so many engines DON'T have it from Lycoming is because usually the airframe manufacturer spec'd and added their own afterward. You pretty much want to have one to protect your $30+K engine.
Stephen Samuelian, CFII, A&P IA, CTO
RV4 wing in Jig @ KPOC
RV7 emp built
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Old 02-09-2011, 06:57 AM
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miyu1975 miyu1975 is offline
Join Date: Apr 2008
Location: Indianapolis, IN
Posts: 1,029
Default unsure

Sorry to rehash this old thread but I have taken position of my IO 360 AIA with bendix FI... I am about to order the FWF kit (minus a few items)....I am trying to figure out if my engine already has or needs a sniffle valve. Where would it be located. sorry for my ignorance...

photo of the engine prior to tear down and clean up..

Ryan Allen, CFII

RV 7 N324TP IO 360 A1A
Flying since 7/2012
Ferry Pilot Services Available
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Old 02-09-2011, 07:09 AM
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Walt Walt is offline
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 4,660

It's on the bottom of the intake sump, looks like an oil drain plug but it's in the intake sump not the oil sump.
Walt Aronow, Dallas, TX (52F) RV7A, IO360, C/S, 1500+hrs

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
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Old 02-09-2011, 07:58 AM
Join Date: Sep 2005
Location: 1T7, Kestrel Airpark , Texas
Posts: 765

Just to throw some thoughts out there for debate.

Forget the water argument for a minute. The valves only purpose is to drain excess fuel that pools in the intake sump.

How effective is that on a taildragger? Just looking at mine sitting here and there is room for a significant amount of fuel to pool at the rear of the manifold.
So, for a taildragger is a sniffle valve really doing anything?

If the valve is installed, by it's very design, will vent any pressure in the manifold that is in excess of ambient cowl air pressure, degrading manifold pressure recovery when the lower cowl pressure is ambient or slightly below.

Bringing back the water argument, a manual valve would seem to sufice. Wouldn't a manual or electric actuated valve be just as useful?
Wade Lively
-8, Flying!
IO-360A3B6D, WW 200RV

Last edited by RV8RIVETER : 02-09-2011 at 08:18 AM.
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