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glider4

Well Known Member
OK, tried reading search results for an hour with no answer for this, checked several builder sites and I can't find anything in my engine manual or the plans that covers it.

I have installed the yellow plastic tubing that fits over the short copper tubing of the fuel overflow valve on my mechanical fuel pump. That mechanical fuel pump is attached to my IO-360 engine.

I'm not sure under what conditions fuel would need to escape through the mechanical fuel pump overflow line. Regardless of that, I don't want that yellow plastic tubing anywhere near my hot Vetterman exhaust pipes.

Is fuel overflow through the overflow valve on a mechanical fuel pump a common event?

But, most importantly, how and where have you routed the yellow plastic tubing to the exterior of the aircraft in a way that avoids the heat from the exhaust?

As usual, thanks in advance to all the experts out there for your help!

Albert Thomas
N880AT
RV-8A QB
Almost ready for the DAR
 
Fuel only comes out there if a diaphragm ruptures. I believe most of the RV's route the line dead center bottom of the firewall?
 
Photo

Found a photo of how I did mine recently. One of the firewall drawings for the -7 shows how the installation is supposed to look. Hope it helps.

1z6yrdg.jpg
 
Gary's routing is common.
Do NOT route it to "center" of firewall. That's much too close to the exhaust.
 
Do NOT route it to "center" of firewall. That's much too close to the exhaust.
Click to expand...

Mel, on the 10 it routes to the lower cowl outlet brace, right in the middle, as per plans.
 
Thanks for the replies!

Mel, I agree that having the overflow vent routed to terminate between the two exhaust tubes does not sound like a good idea!

Gary - I like it! Good location and the transition to aluminum tubing for the last several inches before the exit makes sense too. I am also using the Skybolt firewall/cowling retainers on my -8A so I have the same "step" to exit through. I am assuming you drilled a small hole in the cowling and the end of the overflow tube is sticking out just a fraction below the cowling's exterior surface....

This item is getting addressed this weekend so I appreciate all the timely feedback.

Al Thomas
N880AT
RV-8A QB
 
FWF Plans

This is actually covered in the FWF plans (at least for the -7). The tube actually exits through the flange formed by the bottom fuselage skin and the lower flange on the firewall. That way, the tube protrudes slightly aft of the edge of the cowling - so the cowling isn't involved at all.
 
It's done!

Thanks everyone! Looks almost exactly like Gary's install except on an -8A rather than a -6.

Dan - thanks for the tip on routing on the flange. And, no, it's not covered in my plan set. My primary firewall reference pages are Drawing 21 (10/01), Drawing 31A (6/03) and Drawing 34 (9/97). I have Chapter 11 in my builder's manual (3/02 version) and it's not in there either.

Perhaps it's now in the newer plan sets or perhaps covered in Van's FWF kit which I didn't buy. Anyway, thanks again for the help!

Al Thomas
N880AT
RV-8A QB
 
On my 7 I ran it to the lower corner of the firewall and into the gear leg fairing. There is no issue with the cowl, no metal tube required, and far away from the exhaust.
 
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