Gas Tank Vent Tube - Spewing Gas - Impala Tech
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post #1 of 7 (permalink) Old 05-01-2013, 04:10 PM Thread Starter
 
 
Join Date: May 2013
Location: Twin Cities, MN
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Gas Tank Vent Tube - Spewing Gas

I own a 1966 Impala Convertible.

Sometimes after a cruise my car spews gas out of the gas tank's ventilation tube. It doesn't happen every time but when it does it usually happens 5 to 10 minutes after I turn off the car. If I had to guess I'd say it spits out about 1/4 cup of gas just behind the passenger side rear tire. Any theories as to why this would be happening? Obviously it's a dangerous situation that I want to fix ASAP.

A little about my car. I'm running a 496 BBC (480hp/580tq) with an electric fuel pump and a 5/16" fuel line. It doesn't have a return line. The tank itself is pretty beat up (surface rust and some big dents) and is most likely original to the car.

I've been thinking about replacing the tank, straps, sending unit and changing to a 3/8" fuel line and a mechanical fuel pump. Other posts indicate Spectra makes a good affordable tank. Any suggestions on where to buy the fuel line and fuel pump?

Jeff
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post #2 of 7 (permalink) Old 05-01-2013, 07:22 PM
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Fuel line should be 3/8th inch with a return line. You can buy a brand new Spectra fuel tank from here or a half dozen other locations;

http://www.carparts.com/details/Chev...FUHe4Aod_SEAhg

Look here for a 3/8th pick-up and fuel gauge to fit in your tank

http://www.summitracing.com/parts/oe...FUFo4Aod_nAA2Q

Here's a new gas line in 3/8th inch:

http://www.classicindustries.com/imp.../bgl6502s.html


Big Dave
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post #3 of 7 (permalink) Old 05-01-2013, 07:54 PM
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You need a return line. Also, are you using the original non-vented gas cap or a later sealed one?

Two doors, four doors, wagons, and ragtops.
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post #4 of 7 (permalink) Old 05-01-2013, 08:07 PM Thread Starter
 
 
Join Date: May 2013
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Quote:
Originally Posted by jayoldschool View Post
You need a return line. Also, are you using the original non-vented gas cap or a later sealed one?
Stamped in my gas cap are the words "Not Vented". I've never heard of a "sealed" cap before. Is there a difference?
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post #5 of 7 (permalink) Old 05-01-2013, 08:09 PM Thread Starter
 
 
Join Date: May 2013
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Quote:
Originally Posted by Big Dave View Post
Fuel line should be 3/8th inch with a return line. You can buy a brand new Spectra fuel tank from here or a half dozen other locations;
Is the return line due to the electric fuel pump? I'm asking because I want to give up the electric fuel pump (noisy) and go back to mechnical. Does a mechanical pump still require a return line?
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post #6 of 7 (permalink) Old 05-01-2013, 09:39 PM
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All 65-66 B body cars had a vent tube that ran up into the trunk and back out the bottom ,the cap is non vented to keep fuel from splashing out the back of the car.
There is a short piece of fuel hose where the vent tube comes out of the tank and attach├ęs to the metal line that runs up through the trunk and back. That hose and the fuel line hose should be replaced every couple years as the alcohol in our fuel dries them out very fast. That also goes for all the fuel hose near the motor also. Check your vent hose at the tank.
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post #7 of 7 (permalink) Old 05-01-2013, 11:09 PM
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Quote:
Originally Posted by Diehard50248 View Post
Is the return line due to the electric fuel pump? I'm asking because I want to give up the electric fuel pump (noisy) and go back to mechnical. Does a mechanical pump still require a return line?
Your AC Delco Mechanical Fuel Pump part number 40727 awaits you as it is still manufactured today. This was the same fuel pump that was installed on big block cars back in the sixties.

http://www.summitracing.com/parts/acf-40727/overview/

If you use an electric fuel pump you should use a return line as unlike a mechanical pump that changes volume output to match engine RPM an electric pump moves the same volume of fuel all the time it is on. So at idle you are flooded in fuel and at wide open throttle you are probably starved for fuel.

Big Dave
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