Gas tank venting

[AMiller]

Im getting ready to finish plumbing my gas tank and got to thinking, this usually gets me into trouble.

My gas tank has steel vent line off the top of the tank next to the supply line for the fuel syestem. The dirrections just say the tank will need venting.

My question is am I venting to let air into the tank as the fuel is dwawn out or letting fumes out of the tank as it heats up and expands. I guess the vent could also be for both cases.

Problem I have with this is if the tank needs to let fumes out I dont want the car smelling like gas all the time. The best looking cars in the world are less appealing if the smell like they are leaking gas.

The system Im running is just a electric fuel pump on a carburator. Can I get away with just venting the tank to let air in?

Thanks,

Aaron

[Tim Brewer]

The vent is to let air out when you put gas in your car. Without it, it would take you a long time to put fuel in your tank. The vent tube goes from the tank to aprox. 6" below your feul cap. You will never smell gas fumes.
Tim

[jarendall]

I put a loop in my vent line at the top, I used 3/8 aluminum line which is easy to bend, I ran the vent up next to the filler cap, looped it and back down below the fuel tank, so any overflow will not touch any part of my car, without the vent your gas tank could collapse from the suction of the fuel pump, if your filler cap is not sealed then you can simply insert the vent back into the fuel tank fill line, check to see if your filler cap has a gasket in it.

[Frank Messina]

I took one of those clear inline fuel filters, pulled out the filter and filled it with activated charcoal for a fish tank filter. You'll have to put a little piece of screen at the ends so that the charcoal doesn't fall out. Connect it to the tank with some vacuum line and secure it to the filler almost as high as you can go and with anotheer short piece connected to the other end of the filter double back down the filler pipe about 6". Voila! Vented and no smell.
Frank

[CobraKurt]

Originally Posted by Frank Messina

I took one of those clear inline fuel filters, pulled out the filter and filled it with activated charcoal for a fish tank filter. You'll have to put a little piece of screen at the ends so that the charcoal doesn't fall out. Connect it to the tank with some vacuum line and secure it to the filler almost as high as you can go and with anotheer short piece connected to the other end of the filter double back down the filler pipe about 6". Voila! Vented and no smell.
Frank

Frank- I am havng the gas smell problem/issue.Can you PLEASE post a few picts of your charcoal filter set-up. Thx Kurt

[mickmate]

Keep thinking, you got it figured out. The vent does both letting you fill with fuel and letting it draw out without collapsing the tank. I usually plumb the vent through a tipover valve Jaz 834-206-06 - Jaz Products Fuel Cell External Tip Over Valves - Overview - SummitRacing.com and then a little compressed air muffler McMaster-Carr on the end as high up as you can get it in a fenderwell. You can get a kit to do both tipover and vent from Summit, Speedway etc. Use flexible or rigid tubing to get from here to there.

[WardL]

Regardless if you do something with a charcoal filter or a vent to your intake system I believe you have a smell from gasoline. No worry about it because once you get out of your garage with the engine running. Your normal exhaust will stink much worse than a little gasoline! The smell of gasoline will also be possible from your carb. With the high flow air cleaners & big carbs we have, the smell of gas will come off the carb more than a normal factory carburated vehicle. Add the smell of the leather, a little ethanol and you have one fine smelling Cobra (actually, no joke, you better like it if you are going to have a Cobra). It is not the strong smell of gasoline when you are handling it. The leather seems to make it intoxicating....

The EPA requires new cars to have low tail pipe emissions as well as low evaporative emissions. These evaporative emissions are not well controlled in the typical Cobra.