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Pirep: Sniffle Valve troubles...

bjdecker

bjdecker

Well Known Member
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Earlier this week, upon returning to my home airport, I chopped the throttle turning downwind and heard the signature "Pop-Pop-Poppity-Pop-Pop" of an induction leak. :(

I removed the sniffle valve (Lycoming 75444) and as expected it was stuck "open". I repeatedly flushed with brake cleaner/gun-scrub and soaked in Hoopes #9 to free up the little ball bearing inside.

This is the second time in as many years that it has clogged. I've added a heat shield on the cross-over exhaust header to see if that helped (it didn't).

Questions: Would drilling a slightly larger hole into the existing body help any? Would switching to the AFP version (second pic) be a better solution? Or should I just plug the hole entirely and add "drain sump" to the Oil & Filter change checklist?

Pics for reference:

ea_lw-75444.jpgManifold-Drain.jpg
 
bjdecker said:
Earlier this week, upon returning to my home airport, I chopped the throttle turning downwind and heard the signature "Pop-Pop-Poppity-Pop-Pop" of an induction leak. :(

I removed the sniffle valve (Lycoming 75444) and as expected it was stuck "open". I repeatedly flushed with brake cleaner/gun-scrub and soaked in Hoopes #9 to free up the little ball bearing inside.

This is the second time in as many years that it has clogged. I've added a heat shield on the cross-over exhaust header to see if that helped (it didn't).

Questions: Would drilling a slightly larger hole into the existing body help any? Would switching to the AFP version (second pic) be a better solution? Or should I just plug the hole entirely and add "drain sump" to the Oil & Filter change checklist?

Pics for reference:

View attachment 74328View attachment 74329
Click to expand...
I had the same problem with my -8 (albeit on the ground) and replaced it with the AFP version...never had a problem again.
 
In the 17 years my -6 has been flying, I've never had a sniffle valve (just a pipe plug in the hole). Last time I had intake tubes off to replace gaskets, I shot some pics of the plenum. Tiny bit of oil in the left rear corner and that was it.

If you have a taildragger, you'd need to drill a new hole in the rear of the plenum to get much benefit from a sniffle valve, and I wonder how many peeps here have bothered with that. One hole I did drill is for that blue fitting on the rear wall, which is my manifold pressure source.

One potential benefit for a sniffle valve is to purge rainwater in case you find yourself tied down in a horizontal storm and you neglected to drill a drain hole in the intake snorkel. But again, if you have the valve in the center of the plenum, the rear cylinders would suck in water regardless.

1731618399604.jpeg1731618419800.jpeg
 
No sniffle valves here on either of our injected Lycomings (Tundra - 450 hours, RV-3 - 850 hours). Just saying….
 
I have been considering putting a plug in for a long time. Will do next month when changing the oil. Can someone confirm the thread size? 1/8 plug?
 
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