Physically Impossible

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TrailBeast

AKA Mopars4us on Youtube
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On fairly regular basis I see people post about their car not wanting to fire up after sitting for a day, or days.
“I think my fuel is draining back out of the carb” ends up being mentioned.
This is not physically possible with the average carbs we run.
The fuel would literally have to jump up an air gap and climb back out.

It can drain back down the line from the needle and seat, or evaporate from engine heat after shutdown, but it will never ever ever suck the fuel out of the bowl/s.
That’s about as possible as the existence of the tooth fairy.
 
On fairly regular basis I see people post about their car not wanting to fire up after sitting for a day, or days.
“I think my fuel is draining back out of the carb” ends up being mentioned.
This is not physically possible with the average carbs we run.
The fuel would literally have to jump up an air gap and climb back out.

It can drain back down the line from the needle and seat, or evaporate from engine heat after shutdown, but it will never ever ever suck the fuel out of the bowl/s.
That’s about as possible as the existence of
the tooth fairy.

I don’t know about draining out but I have had the bowls be empty after sitting for a while. Doesn’t take heat, gas will evaporate over time, which is what I’ve always chaulked it up too
 
I don’t know about draining out but I have had the bowls be empty after sitting for a while. Doesn’t take heat, gas will evaporate over time, which is what I’ve always chaulked it up too
Exactly. Evaporation
 
Idk man. A quarter miraculously showed up in place of every tooth I ever lost when I was a kid. At the rate of inflation, I can't wait for my teeth to start falling out again in another 10-20 years. There's got to be a 71 Cuda in there by then if I lose them all at the same time.
 
I don’t know about draining out but I have had the bowls be empty after sitting for a while. Doesn’t take heat, gas will evaporate over time, which is what I’ve always chaulked it up too

Exactly. Evaporation

I agree that it evaporates eventually even without engine heat, but it’s the people that say it drained back to the tank from the bowls I’m referring to.
 
I fully agree with the statement," gas cannot be sucked out of the carburetor bowls". But still the gas can be sucked back into the tank, leaving the fuel lines and pump dry. When the gas tank cools down their is a bit of a vacuum that takes place, especially when the gas tank vent cap is not working or if some of the emission vacuum lines are plugged and or removed. I installed a check valve in the fuel line just to stop this sort of thing....
 
That's why I put an axuilary electric (flow thru) fuel pump on my Barracuda. I turn the key to "on" then flip the fuel pump switch....let it pump up the fuel to the carb (and mechanical fuel pump), it helped a lot.
 
When I owned the 56 coronet with a 291 hemi, that sucker needed a prime every time. Big ol cast iron intake seemed to hold the heat and had a tiny two barrel, so not a lot to evaporate.
 
Thnx Trailbeast, I was gonna tackle that last nite, - imagine, water in your sink jumping back up to the faucet to drain !
 
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On fairly regular basis I see people post about their car not wanting to fire up after sitting for a day, or days.
“I think my fuel is draining back out of the carb” ends up being mentioned.
This is not physically possible with the average carbs we run.
The fuel would literally have to jump up an air gap and climb back out.

It can drain back down the line from the needle and seat, or evaporate from engine heat after shutdown, but it will never ever ever suck the fuel out of the bowl/s.
That’s about as possible as the existence of the tooth fairy.
I have only seen one exclusion. My buddy was putting new 6pk carbs on a Challenger. It wouldnt start after sitting a day. The center carb had a very small casting flaw that allowed the fuel to leak out
 
I have only seen one exclusion. My buddy was putting new 6pk carbs on a Challenger. It wouldnt start after sitting a day. The center carb had a very small casting flaw that allowed the fuel to leak out
Friggen' Holley's!
 
Wait a minute, the tooth fairy isn’t real?!?


I'm not going to be the one to tell him!

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The problem is the ethanol in the fuel evaporates very fast. Its really a problem on the edelbrock/carter carbs. I pulled a carb apart after 2 days and the bowls were bone dry with only a little brown substance left in the bottom.
 
Friggen' Holley's!
I bought a bunch of Holleys thinking I was going to clean up rebuilding and flipping. Unless it is a double pumper, i havent been able to give them away, I just sold a very clean, rebuilt 750 vac sec that was posted for a month for $100. I think the problem might be one of several things, the market is flooded with Holleys, or holly quality control has gone down, or They are making copycat Holleys that offer more opportunities for tuning, for a Good price, new
 
Forced Alky fuel mix is the stupidest farce forced upon the U.S. ever. When I ran the carb on my 67 (vs EFI), I used a carb insulator, DIY vapor return system, and rear mount electric pump. It helped a bunch. 'N yeh, I used an Edelbrock carb.
 
boils out of a carter on a cast iron intake. Every morning my electric carter pump would run load free for about 4-5 seconds. If I tried to start it without the pump on it would run for about 5 seconds and then sputter and die. Fuel was going somewhere and on a carter it can only evaporate. My Nikki 2bbl with clear sight glass will hold fuel for about a week at the level mark. The facet style 'jiggler' electric pump fills it and there is a tap with a check valve that sends the fuel back when the bowl is full. Todays fuel will evaporate and leave a white jello like crap. Lawnmowers are notorious for getting their bottom bowl jets clogged with this crap.
 
boils out of a carter on a cast iron intake. Every morning my electric carter pump would run load free for about 4-5 seconds. If I tried to start it without the pump on it would run for about 5 seconds and then sputter and die. Fuel was going somewhere and on a carter it can only evaporate. My Nikki 2bbl with clear sight glass will hold fuel for about a week at the level mark. The facet style 'jiggler' electric pump fills it and there is a tap with a check valve that sends the fuel back when the bowl is full. Todays fuel will evaporate and leave a white jello like crap. Lawnmowers are notorious for getting their bottom bowl jets clogged with this crap.
Exactly, put some E-10 in a quart jar and watch how fast it disappears. Some 2 barrel carbs have bowl vent's that are sealed until the throttle is opened. Those aren't as effected by evaporation. A cast carb on a iron manifold that is at 200° with ethanol inside that boils at 155° and here lies the problem.
 
Just because you can't see something, doesn't mean it does not exist, or is impossible. You can't really SEE the air you breath in, right? The Tooth Fairy is real! ...and I don't care WHAT you say!
 
With 180* or 190* T-stat, when you shut down and walk in the house, she will spike to around 210* -215*F. Anyone with a carter who thinks they have it bad, should see the tiny fuel capacity of a Quadrajet. Especially the early Quadrajet.
 
Just because you can't see something, doesn't mean it does not exist, or is impossible. You can't really SEE the air you breath in, right? The Tooth Fairy is real! ...and I don't care WHAT you say!
exhale in 20F weather.....:rolleyes:
 
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