sniffle valve required?

[dromuald]

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?

[Bavafa]

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.

[bjdecker]

It would be interesting to measure how much residual fuel, oil, stuff, has accumulated in that sump after all these years...

[BillL]

Originally Posted by bjdecker

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 . . .

[vic syracuse]

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

[JonJay]

Probably should note to casual readers that a sniffle valve is for horizontal injection, not vertical.

[rswalden]

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!
Cheers,
Waldo