Upgrading to 3/8 fuel line

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wafastr

wafastr

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Doing a restomod on a 70 dart, s6 to 360. Considering a 3/8 fuel line with no vapor return line. Also wondering if the stock tank, with its factory 4 hose vapor vent system, would work okay with an unvented factory style painted gas cap. I think it should be okay. Any advice out there?
 
The 4 tank vents that year were designed to go up to the vapor separator tank in the trunk. If you eliminate that, and just hook one or more to a vent of some sort, you may create a "puke" or "siphon" situation. If I were in your shoes I would put a vent line branched into the filler tube like the non CA 70 and the 69/ earlier cars. This was simple and works well.

What is not clear in this diagram is that the vent tube bends up and goes clear up to the top of the quarter panel, then down along the filler tube, through the gasket, and open ends just inside the rear frame rail

2cmugso.jpg
 
3/8" is only for race cars. You're wasting your time on the street. Removing all the vapor vent system and installing a vented cap should work as far as I know.
 
Murray said:
3/8" is only for race cars. You're wasting your time on the street. Removing all the vapor vent system and installing a vented cap should work as far as I know.
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I would not run a vented cap. Construct a proper vent system, not that hard. And then you don't have to worry about gas puking down the side of the fender
 
I will stay with the 5/16" fuel line. A Hemi or dual quad big block may need a 3/8" line but probably not a 360. Would the existing vapor vent system work well enough to allow fuel to flow to the fuel pump and adjust for expansion in the fuel tank if I just cover the end of the vapor line (that originally went to the s6 breather cap) with screen to allow air movement in that line? Thanks for your replies.
 
wafastr said:
I will stay with the 5/16" fuel line. A Hemi or dual quad big block may need a 3/8" line but probably not a 360. Would the existing vapor vent system work well enough to allow fuel to flow to the fuel pump and adjust for expansion in the fuel tank if I just cover the end of the vapor line (that originally went to the s6 breather cap) with screen to allow air movement in that line? Thanks for your replies.
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You could. Leave the line HIGH to prevent siphon. Another thing you could do is tee it into the breather to the filter bonnet. Will help keep fumes at bay
 
If I was going to all the trouble to make new fuel lines I wouldn't bother with 3/8 line. I go right to 1/2 and be done. A bigger fuel line won't hurt you. Ever. Especially if you are using a mechanical pump.
 
Unless he's building a 600+hp monster, that is overkill. The size alone is enough to discourage me, 1/2 is much more difficult to work with, and I used to fiddle with HVAC service, back in the day. I still have my 3/8, 1/2, and 5/8 benders, and may have a 3/4 somewhere
 
67Dart273 said:
Unless he's building a 600+hp monster, that is overkill. The size alone is enough to discourage me, 1/2 is much more difficult to work with, and I used to fiddle with HVAC service, back in the day. I still have my 3/8, 1/2, and 5/8 benders, and may have a 3/4 somewhere
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If you use aluminum tubing it bends real easy. Steel tubing...not so much.
 
If the lines need replacing (kinked, rusted thru, bent ) then upgrade to 3/8. If they are fine then stick with 5/16 and use the money saved somewhere else in the build. Just my opinion.
 
Good point, I’m running an electric pump so I have 3/8 fittings. Most cars ive seen with the 3/8 line have 5/16 to the carb
Some of the mechanical hp pumps come 3/8 and others have removable fittings, in which case you would size the fittings accordingly.
 
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