79 gas tank pressure

I have a 1979 vette. It sat in my garage for a few years, was not drove.
Carb needed to be rebuilt, I decided to buy a new one. When I took the gas
line off of the old one, gas sprayed out. Took the gas cap off and released the pressure from the gas tank, it stopped. Never really thought much about it.
The carb was off the car for a couple days. Came home from work one day and smelled gas when I pulled in...Gas smell even in the house...Went out in the garage, the gas line was dripping gas....a bunch of gas, was all over the floor under the car. I again took the gas cap off and released some pressure, it stopped...
Is this normal?? Is there a vent on the gas tank some place that may be stopped up??? Maybe bad gas cap???
New carb is installed, car is running fine, but this just bothers me a bit.
Thanks!!! Roger
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If the cap is like the one on my 69, it lets air in but not out. Temperature changes will put a slight pressure on the tank.
Al
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Thanks for the response Al....
Slight pressure with temperature changes I would agree with, but enough to drain a lot of gas??? The floor was wet underneath the car, it drain a bunch of gas.
Maybe I am worring about nothing. Just don't want to see my car that I have owned for 16 years go up in flames...Not to mention my house :-)
Thanks!!! Roger

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Depends on how much fuel is in the tank and how much temperature variation there is. Yes, it will force the fuel out of the tank.
Al
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I don't know about the pressure in your fuel tank (slight or a lot) but your leak may be the rubber fuel line that connects to the fuel pump from the steel lines that are mounted to the frame. Three years ago the rubber fuel line that connects the fuel pump return line to the top of the fuel tank sprang a leak on my '75, and sprayed gas all over the inside of the right rear wheel well while I was out for a drive. Lucky I didn't turn into a fire ball going down the road. Had to take it to a shop and drop the gas tank to replace both rubber connector lines. Also replaced rubber lines at the fuel pump. Your '79 might have dry rotted rubber lines.

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Roger Smallwood wrote:

the fuel line leak and check for a problem with the Evap cannister, cannister filter or purge valve. Check for a replaceable filter on the bottom of the cannister. Failed to change that filter on a '79 Pontiac and had similar problems--lots of pressure in the tank. The first owner's body shop had spliced fuel line with hose and couplings. Started leaking when car was 12 years old and engine not running. Evap cannister was about 1/2 full of liquid gasoline. That car (Calif emissions) had a multi-port vacuum switch in a hose between the carb and the cannister. Threw parts at the problem. Replaced the cannister, cannister filter, vacuum switch and hoses to the cannister. Snugged up the splice in the fuel line--all was OK after that. (told next buyer about the splice.)
Every time a storm goes through, both barometric and temp changes will play with pressures in the system. Don't recall if there was ever negative pressure in the Pontiac tank--think it was usually positive. The C4 and C5 always have positive pressure.

Sounds like a reasonable concern.
Don't know if the '79 'vette had "roll over" valves in the fuel system. If so, those might be worth a look.

--
PJ
Floor crawler with Oak side rails
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wrote or did cause to be written:

I'll second that. Had a similar problem with the ECS canister. That canister should be venting any pressure in the tank. Pull the hose connecting it back to the fuel tank and see if it is plugged or full of gas.
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