Air filter box fuel drain???

[hlangebro]

I have a O-320E2A that was been modified into a D3G, 160HP.
The mechanical fuel pump has a drain line, but I seem to have seen on other engines that the carb itself has an overflow/drain line, but I dont have that on mine...
I was thinking about making a 1/4" drain with a hose, at the far bottom of the airfilter box/bowl, in case the air filter box gets flooded. I have heard this has happened to quite a few people, with disatrous results...
Does anyone have any ideas regarding this?

[RV6_flyer]

There is no drain line on the carb. There is a PLUG in the carb that can be used to drain the float when it needs serviced.

My RV-6 has been flying 15-years. I have a #30 hole drilled at a low spot in the fiberglass of the FAB to drain any fuel that accumulates. IF you do NOT pump the throttle without the engine cranking, you should not get any fuel in the FAB to drain out. IF you pump the throttle without cranking the engine, you WILL get fuel accumulating in the FAB.

[Rupester]

My approach was the same as Gary's ... a # 30 hole in the bottom.
A fancier and more expensive solution - I think - is to install a sniffle valve. Isn't that their purpose ? .... to open a drain in the intake manifold when the engine shuts down, and close the drain whenever the engine is running? This prevents the accumulation of fuel that could/would run down into the air filter box. That's my understanding, anyway. Somebody correct me if I'm wrong.

[Mel]

The drain hole in the air box is also there to prevent water collecting in the box when parked in blowing rain or when washing the airplane.

[Janekom]

Onour RV10 I have also made a #30 hole towards the rear/low end but I have seen other plumbing a pipe from that hole they made in the FAB.

[AlexPeterson]

If you do choose to put a fitting for a hose on the bottom of the airbox, but inside the filter, do think carefully about how to make it impossible for anything to come apart and take a ride through the engine. I made a drain (inside the filter) with a hose by prosealing a fitting to the outside of the airbox, with nothing at all on the inside. I turned the fitting on a lathe, sort of a top hat shaped part.

[hlangebro]

Yes, that was what I was thinking about to. It has to be outside the FAB, sort of a small funnel shape and then a small tube and a hose.

[Pmerems]

I have an RV-7A with a vertical inducted IO-360 and originally had holes in the FAB per the plans. However I noticed a small amount of a "liquid" accumulating on the top of my nose wheel pant. It appeared to be a combination of gas and oil. It wasn't always there but I had to clean the pant from time to time. I chased it to the fuel coming out of the drain holes in the FAB dripping onto the nose gear leg traveling down the leg and dripping on the pant. I believe after shutdown excess fuel drains into the FAB as well as some hot start techniques (flooded engine technique) also cause some accumulation.

I decided to bond an aluminum tube on the bottom of the FAB and run a rubber hose aft near the lower cowl center support.



I personally know of an RV-6A that had a FAB fire on start-up due to the residual gas accumulating in the FAB. I believe he did have drain holes but maybe in the wrong locations. Damage was minimal. He too bonded in a tube similar to what I did to prevent any future problems.

I hope this helps.

[Clouddancer]

Paul,

I like your idea of the bonded tube. I would be interested to know the reason for the crimped end on your aluminum tube? Some sort of a restriction?

[Pmerems]

I chose to crimp the end of the tube to "shut off" the end. I didn't want to rely on epoxy to plug the end. It also "tapered" the end of the tube which made it easier to glass in and transition to the air box.