# 66 gto fuel and vapor line



## sixtysix (Jul 2, 2010)

While climbing around my project, I noticed two lines coming from my gas tank sending unit. I did some research, and found that on a 66 gto, it uses a vapor line that goes to the fuel filter. This application is only called for on a vehicle that is equipped with factory air, which mine has. The vapor line on mine was capped off by the previous owner. What is the importance of this line on an AC equipped car?Plese help. If it isnt necessary, I will keep it capped off.

Thanks


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## lars (Sep 28, 2004)

The return line is not vapor return - it's fuel return. On an A/C car, there is much more heat in the engine compartment, and the fuel system had a tendency to vapor lock. The fuel return line keeps cool fuel moving through the fuel lines at all times, solving that problem.

With the properties of today's fuels, a fuel return line is almost essential for reliable operation of a carbureted engine: I spend a lot of time and money setting people's cars up with fuel return lines to solve hot weather drivability problems. If your car already has a fuel return line on it, 'fer chrissake, use it. It would be silly to cap it off rather than taking advantage of the fuel return system design.

(See my multiple posts in this Forum with photos of fuel return line systems I have built - all requiring extensive and expensive lines to be installed - you can simply hook yours up)

Lars


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## geeteeohguy (Feb 2, 2008)

Lars is, of course, right. My '67 came with vapor return although it has no AC....just the HD cooling option. I disconnected it at Craters of the Moon on the side of the road broken down in '88 (turned out to be a collapsed fuel sock) and only reconnected it last year. Re-connecting it solved ALL of my "hot fuel" hiccups. If you don't want to buy the $40 repro filter, buy the all silver colored generic one for $11....that's what I did. All the stuff is available from the vendors....the second line (that attaches to the timing cover),the filter, the filter bracket, etc. A job _well_ worth doing.


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## pontiac (Mar 6, 2011)

buy the fuel pump with the dual outlets and use regular fuel filter.


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## geeteeohguy (Feb 2, 2008)

That will work just as well, and easier to plumb, too. Not "correct" though.


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## lars (Sep 28, 2004)

The closer you can get the return line to the carb, the better the system works: The return-style pump makes an easy, clean installation, but the external filter with the "third nipple" return feature, located close to the carb inlet, actually works a little better in keeping cool fuel circulating up near the carb. :cheers

Lars


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## geeteeohguy (Feb 2, 2008)

I did not know that, but it makes sense....a lot of heat in that small area from the pump to the carb,more so than at the fuel pump...so a diversion right in front of the carb would transfer more heat.


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