Gas cap type - Impala Tech
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post #1 of 6 (permalink) Old 06-16-2009, 03:10 PM Thread Starter
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Gas cap type

Should I use vented or non-vented gas cap for 1970 impala? I got a locking cap at AutoZone but I am not sure it is exact fit as I have to struggle to get it in or out.
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post #2 of 6 (permalink) Old 06-16-2009, 04:52 PM
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Vented or non-vented used the same gas cap attachment so they are interchangeable as far as getting them to fit the filler tube. If you have a charcoal filter and a return line you use a non-vented cap. No return use a vented cap to keep from crushing your gas tank with the vacuum the pump could cause.

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post #3 of 6 (permalink) Old 06-16-2009, 09:20 PM Thread Starter
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Is there an easy way to check for the charcoal filter or the return line? My wagon has the tank behind the left rear wheel. I would have to remove the cover on the inside if I were to have a look at the tank itself.

Thanks.
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post #4 of 6 (permalink) Old 06-16-2009, 10:46 PM
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Hey Alex,

Neither of my 70 Impalas have a charcoal cannister. But if memory serves me correctly, the can was on the left side right in front of the voltage regulator. Also both cars are equipped with non-vented caps....never had any problems. Aftermarket locking caps seem to be made....WRONG!!! Just enough to be a hassle.
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post #5 of 6 (permalink) Old 06-17-2009, 06:49 AM
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You can always use a vented cap as it won't hurt anything but the environment as your fuel evaporates. There should be a 5/16th hard line up to the left front fender where they mounted the charcoal canister (vent) to the gas tank. From there there were two rubber lines that went to the manifold (one was a fume tube to suck out the gas tank fumes and the other was a vacuum line to open the valve inside the charcoal canister only under engine power).


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post #6 of 6 (permalink) Old 06-17-2009, 09:07 AM Thread Starter
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Thanks guys. I will check that once I get home. I went thru 3 gas tanks with the non-vented aftermarket cap and the tank did not collapse yet, so I think I am good (or I have a hole in the tank that acts as a vent )
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