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Fuel Vent

When you buy Atlee Dodge caps they ask it your run car gas or not. Blue gaskets 100ll. Black ones are for car gas.

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Thanks for all of the replies. He replaced caps and all is good. ������
 
I'm not seeing that on the Atlee Dodge website. It only shows a pic of the blue gasket, and no mention of an alternative for mogas?
http://www.fadodge.com/fuel-cap-vented/

Sorry I don't buy the gasket swelling story. The caps are drilled in the inside center area and a cupped ss spring keeps the seal from blocking the vent. I've run mo gas for decades with full tanks have never had a blocked vent. These Atlee caps are very high quality. Piper had problems with their caps over the years. A friend of mine who when he was ferrying new Cubs from the factory, ran into caps that weren't drilled properly when new. I wouldn't run a goose-necked cap unless I absolutely had to. They suck in a bunch of undesirable things...
 
Sorry I don't buy the gasket swelling story.

Nanook - If we pulled into your shop with a cub that had it's stock tank collapsed and an Atlee cap on it what would you think was the cause? Vent issue?

Keep in mind that after blowing the tank back up that cap was used for the entire time and no issues. If the cap had been plugged by some other cause the problem of tank collapse would have persisted. It did not.

Then there is part where Atlee offers an alternative gasket for use with auto fuel. Why, if there was no problem to begin with. Even Atlee himself said the cap should not be used with auto fuel.

I'm not trying cast any dispersion on the Atlee caps because this was a situation where the wrong fuel plus a particular set of circumstances caused the event. The fact that you have run for decades with auto gas and Atlee caps with no issue doesn't surprise me at all because of the low probability of this event to happen in the first place.

Jerry
 
We never had ethanol in gas that I know of. City gas DID used to have MTBE (methyl tertiary butyl ether) added to oxygenate the fuel. Sometimes it found its way into Valley gas stations. That stuff played hell on lots of equipment.
 
We never had ethanol in gas that I know of. City gas DID used to have MTBE (methyl tertiary butyl ether) added to oxygenate the fuel. Sometimes it found its way into Valley gas stations. That stuff played hell on lots of equipment.

That fits my recollection of things too. There were plenty of rumors about ethanol but as I recall there was a moment when there was MTBE to be found but I don't think that has anything to do with this just knowing the person involved and how careful he is about where he gets his fuel. There is always that possibility though.

Jerry
 
Why do you need ram vents on a 150hp airplane?
I'm not sure about SCs but the 150 HP fuel system in a Pacer will not meet CAR 3 fuel flow with out the pressure tube. Who know how Piper got it passed. Ed Trimmer discovered this when he STCed 180 HP in the Pacer.
 
There;s more than one kind of Atlee cap I think. Vent tube and regular vent. You need to be specific when having this discussion. For my money,. the vented cap with tube out the top is the only sure method.
 
I'm not sure about SCs but the 150 HP fuel system in a Pacer will not meet CAR 3 fuel flow with out the pressure tube. Who know how Piper got it passed. Ed Trimmer discovered this when he STCed 180 HP in the Pacer.

The header-tank fuel system that Piper designed for the PA-18, kept a positive head to the carburetor as long as you used the left wing tank. For cruise configuration the right wing tank & header was adequate. Both right & left fuel tanks required a vented cap only, no ram air caps were/are needed.
 
...Keep in mind that after blowing the tank back up that cap was used for the entire time and no issues. If the cap had been plugged by some other cause the problem of tank collapse would have persisted. It did not.
Jerry
Did it ever occur to you that it is possible, due to many fuelings over time both with a gas hose and a Jerry can that the filler portion of the tank may have been pushed down a little? When this happens the vent in the cap can be pressed against the cover filler neck gasket thus blocking the air vent. Over time you may not even realize that the filler cap was lower than it should be.

Some gas caps are very close to the top of the wing. Enough so that it is difficult to handle the cap.
 
Did it ever occur to you that it is possible, due to many fuelings over time both with a gas hose and a Jerry can that the filler portion of the tank may have been pushed down a little? When this happens the vent in the cap can be pressed against the cover filler neck gasket thus blocking the air vent. Over time you may not even realize that the filler cap was lower than it should be.

Some gas caps are very close to the top of the wing. Enough so that it is difficult to handle the cap.


This was not the case. If it were the venting issues would have been constant. I know we looked things over and there was no issue with the cap conflicting with the cover gasket. The cap was used on that tank for the rest of the trip and in fact he used this cap and tank combo for years after the incident. The tank was not pushed down a little, it was wadded up way down in side the tank bay. When we blew the tank back up it never fully returned to it's original condition so from then on his filler cap set lower and at an angle but vented just fine.

Jerry
 
The header-tank fuel system that Piper designed for the PA-18, kept a positive head to the carburetor
Maybe that's why my 12 has the snorkel vents in the caps. I don't have a header tank. Haven't looked too close but with the Air research tanks, there is an outlet both front and back with lines going to a Dakota fuel valve. Pretty much like my 54 180 except it doesn't have forward tank outlets. It still has one above the cabin snorkel vent.
 
As it so happens..., I now have six (6) fuel caps that are new..., I only need two! I have four from Dakota Cub (two with the "lolly Pop" and two without). I also have two from Atlee that I think I will use...., any interest?
 
Read thru this & several other similar threads, trying to solve a problem I had with my cub after this year's extensive annual & engine swap. Right side tank had a pressurization problem, would initiate fuel starvation/involuntary leaning after flying on that tank for a period of time (no problem on the left). Had what looked like the original caps from the 50's, found that neither cap had been modified per the AD issued in the 50's, cap on the right side had rusted internal parts; replaced both with the milled aluminum caps from Univair @ $100 each. Additional flying showed the problem persisted, fuel starvation on the right tank only. Did find info on this site about a possible low pressure area on top of the wing causing the problem, at least on the one side. Also found a comment about one tank being slightly elevated relative to the other, perhaps adding to the problem. Took the tank cover panels off, examined both tanks and did find one that was higher (the right tank). At the same time, I tested the caps by pressing down on & releasing pressure on each (capped) tank, could hear air expelling as I pushed down and being inhaled as I released pressure on each tank; caps (both original and new) worked as designed. However, I had attached new felt strips to the straps securing each tank (replacing ancient duct tape) and in the case of the right tank, I speculated it was likely the tank cover was putting undue pressure on that tank due to the addition of 1/8" of felt, would not allow the right tank to fully re-expand as fuel was consumed & created low press within the tank as a result; removed the felt, reassembled and flew the airplane. Problem solved, no more symptoms. Anyone having what they perceive as pressurization issues would do well to test the tanks/caps as I did to narrow down the problem, which in my case was never the caps, just my own well intended but ill thought out mod.....
 
Will Univair's $100 milled aluminum caps handle 180hp? I'm using snorkel now. Milled aluminum are beauties.
 
Will Univair's $100 milled aluminum caps handle 180hp? I'm using snorkel now. Milled aluminum are beauties.

Which 180 hp STC do you have? I know Cub Crafter's requires the snorkel type caps. Can't remember on the AERO (Penn Yann) STC.

As far as the felt Piper used 1/16" SAE50 felt. This is the best thing I have found to be the right thickness and crush. I found a vendor although they only sell in mass quantities and I started selling it in kits. https://www.freewebstore.org/pierceaero/Felt/cat158561_115078.aspx
 
Thanks, Steve. I should have mentioned I'm Bushmaster 180hp experimental, using snorkels in the air and Univair's parked because they seal better against moisture. After months on the ground in our relatively cool/moderate climate, I've drained little more than a couple tablespoons of water from the five drains, almost always from the port tank. It would be a shame to use snorkels if the beautifully crafted Univairs would keep the engine running!
 
King, what about something like this on the vent tube? Make a small leather gasket to seal the end when it's closed.

INAS718_220_1.jpg
 
Thanks, Steve. I should have mentioned I'm Bushmaster 180hp experimental, using snorkels in the air and Univair's parked because they seal better against moisture. After months on the ground in our relatively cool/moderate climate, I've drained little more than a couple tablespoons of water from the five drains, almost always from the port tank. It would be a shame to use snorkels if the beautifully crafted Univairs would keep the engine running!

The Univair caps are spiffy (now there's a word you don't hear anymore!) but the snorkels are required on the 180 due to the strength of the fuel draw, from what I understand. Just for the hell of it, I ordered a pair of the $7.95 el cheapo caps from Wag Aero...they are vented, they do fit & if a person wanted something to use just for storage, save yourself $92 each & use these. I don't doubt you could probably fly with them (for other than the 180) and not have any problem, except they're not PMA.
 
Towed banners at a very high power setting all day in a 180 horse super cub had to use full power the first hour or so with a 65' high panel when the wind was off land knocking me all over the place.. anyway we never used ram tube caps just plane old wag aero cheapo vented 7.95 caps, wide open 180hp O-360 and engine never hiccupped.. wonder why you need more fuel flow than the engine can take?
 
One of them there government things.

§ 3.434 Fuel flow rate for gravity feedsystems. The fuel flow rate for gravity feedsystems (main and reserve supply) shall be 1.2pounds per hour for each take-off horsepower or150 percent of the actual take-off fuelconsumption of the engine, whichever is greater.

DENNY
 
As a practice I always remove my vented caps and put a sealed cap on when the airplane sits outside. No bugs, bees, mud dobbers clogging my vents. Its just part of my pre-flight when adding and checking fuel. ADK
 
As a practice I always remove my vented caps and put a sealed cap on when the airplane sits outside. No bugs, bees, mud dobbers clogging my vents. Its just part of my pre-flight when adding and checking fuel. ADK

So......as the temp goes up and down during the day/night where does the + and - pressure come and go from?

Glenn
 
I installed a Biplanes, Inc 12 gallon tank in the right wing of my 11. Those tanks come with and the STC requires, the "snorkel" vented cap. I assume that is because of the method of plumbing the tank into the fuel system. Mine was plumbed similar to a SC system instead, with the deviation noted in the 337.

In any case, in the first couple months, everyone who saw the plane asked why a snorkel on one side, but not on the other. So, I installed a snorkel cap on the stock tank. Nobody has since asked why I have those caps......go figure.

i like the snorkel caps, though....it'd be pretty hard to plug a vent with them....not impossible, but...

MTV
 
One of them there government things.

§ 3.434 Fuel flow rate for gravity feedsystems. The fuel flow rate for gravity feedsystems (main and reserve supply) shall be 1.2pounds per hour for each take-off horsepower or150 percent of the actual take-off fuelconsumption of the engine, whichever is greater.

DENNY

It has been awhile since I worked on a 180hp conversion, the fuel line diameter needed to be the next size up to meet the fuel feed requirements. The goose-necked caps were a quick fix for if you were using the original fuel system lines. The positive pressure flow made up for the smaller diameter gravity feed rate.
 
It has been awhile since I worked on a 180hp conversion, the fuel line diameter needed to be the next size up to meet the fuel feed requirements. The goose-necked caps were a quick fix for if you were using the original fuel system lines. The positive pressure flow made up for the smaller diameter gravity feed rate.

That makes sense than because the towing super cubs were restricted cat and all rebuilt with newer larger fuel line, I have 1,000 + hours towing in several 180 hp super cubs and never used a gooseneck cap, just plain old wag aero style vented caps
 
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