wrong gas cap? - Impala Tech
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post #1 of 7 (permalink) Old 02-25-2009, 05:02 PM Thread Starter
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wrong gas cap?

I did not even know where to post this one . . . I passed a co-worker a few days ago on my way to the office. He said, that while it sounded "kick-***", (1966 Impala, 327, flowmaster duals, total sleeper) he smelled raw fuel as a passed. I checked the fuel system - nothing.

I checked the orginal equipment gas cap and saw signs of leakage. It made sense, accelerate quickly, gas splashes to the back of the gas tank, then leaks out of the gas cap. So, I bought a new gas cap that was supposed to be a correct replacement.

This is my problem . . . the leaking stopped, but the gas cap seems "sucked on" when I go to fill it up. The last time I put gas in it I had to use a pair of channel locks to take it off.

I put the old one back on for now. What in the world would cause this?
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post #2 of 7 (permalink) Old 02-25-2009, 10:16 PM
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Sounds like you need a vented cap, or something wrong with your tank vent.

http://www.impalas.net/forums/image.php?type=sigpic&userid=521&dateline=14693626  69
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post #3 of 7 (permalink) Old 02-26-2009, 03:52 PM
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Quote:
Originally Posted by greenimpala View Post
I did not even know where to post this one . . . I passed a co-worker a few days ago on my way to the office. He said, that while it sounded "kick-***", (1966 Impala, 327, flowmaster duals, total sleeper) he smelled raw fuel as a passed. I checked the fuel system - nothing.

I checked the original equipment gas cap and saw signs of leakage. It made sense, accelerate quickly, gas splashes to the back of the gas tank, then leaks out of the gas cap. So, I bought a new gas cap that was supposed to be a correct replacement.

This is my problem . . . the leaking stopped, but the gas cap seems "sucked on" when I go to fill it up. The last time I put gas in it I had to use a pair of channel locks to take it off.

I put the old one back on for now. What in the world would cause this?
Prior to the EPA requiring charcoal canisters under the hood to absorb gas fumes (good for about seven years worth of fumes anyway) cars like yours had a simple steel can called a gas tank. It was just as sophisticated as the plastic gas can used for your lawn mower. It had a hole to suck out gas at one end and a hole in the gas cap to let air into the tank to replace the burnt gas.

If you use a modern (or as the counter guy said correct replacement) sealed gas cap you can crush your gas tank just like we used to watch "Mr Wizard" do on TV with a one gallon can with a little boiling water in the can. Turn off the heat seal the can and watch it crush from atmospheric pressure as the internal pressure drops.

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post #4 of 7 (permalink) Old 02-26-2009, 05:25 PM
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I'm pretty sure, but not positive, that if you're referring to the green 66 in your profile that it should be a vented tank.
The reason I think that is that as I have been under my own 66, I'm pretty sure I noticed the vent line going up several inches up into the trunk area, by the passenger side wheelwell. You could check to see if you have that also, and whether someone has clogged it up.
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post #5 of 7 (permalink) Old 02-26-2009, 05:50 PM
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Hey Jim,

BA is right both of my 70's are built that way....Both gas caps imprinted "Not Vented".
I cannot say how far back in time when doing that started. Good Luck
Gary
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post #6 of 7 (permalink) Old 02-27-2009, 09:09 AM Thread Starter
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Quote:
Originally Posted by BA. View Post
I'm pretty sure, but not positive, that if you're referring to the green 66 in your profile that it should be a vented tank.
The reason I think that is that as I have been under my own 66, I'm pretty sure I noticed the vent line going up several inches up into the trunk area, by the passenger side wheelwell. You could check to see if you have that also, and whether someone has clogged it up.

Yep, that's the one. I will check the gas tank vent and see what's going on with that. The other theory I came up was that gas may have blew out of the exhaust. When I passed my co-worker, I was all over the gas like a cheap suit! I mean was crusing, high RPM, all 4 barrels open. Could the all open 650 CFM carb delivered too much gas for the 327 to handle?

I usually do not drive her like that, but I just could not help myself. She was spotless, the weather was nice, and the radio was turned up. I had to!

Last edited by greenimpala; 02-27-2009 at 09:38 AM.
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post #7 of 7 (permalink) Old 03-03-2009, 11:18 AM
BA.
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funny.lol.
It is GOOD to give in to the Dark Side. You will be ok.

I don't think there's anyway the gas came out via the exhaust. 650 is a perfect size for a 327.
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