Hard fuel lines

Question why do you use inverted flare fittings on automotive lines, A normal flare is used in home construction for LP and natural gas lines. And vapor gas should be harder to contain than liquid gas. House gas is 6 psi and carbs are 6 psi.

I want to plumb my 3-2 Rochester set up with hard lines thats why I'm asking.

Jim H

 

One word . Vibration !!You dont have vibration on the line to your stove or heater.

 

What's this "flare" of which you speak?

Doc.

 

heres how I did it. just like stock, but bigger line.

 

I run single flare (AN's are single flare) on my musclecar's fuel pump with no problems...
A big reason for running inverted flare is because straight brakeline sticks comes already flared.....so why change it?

 

Brake lines are required to be double flared and I think that is the main reason that we double flare the rest of the steel lines on our rigs. In the past 48 years I have never put a single flare on anything I worked on.

Once a guy learns to double flare a line it becomes second nature when making up lines and I have always felt that it would hold up better and give a better seal over a single flare.

 

I don't like the look. They just don't look like a professional automotive installation to my eye. I don't recall ever seeing flare nuts on any factory fuel lines.

 

They come with inverted flare fittings from the factory. Both GM trucks I have with TBI are inverted flare.
And the theme for my Falcon project is I'm building it in the winter of 63-64. so the plumbing has to look the part, along with every thing else on the car.
Also I'm not a fan of using rubber fuel line for gas lines.

 

I made up the fuel lines for my Pontiac dual-quad setup using brass inverted flare fittings, just like the factory used. I used 3/8" steel brake lines to make the fuel lines. NAPA carries a great selection of the brass inverted flare fittings.





The factory Pontiac Tri-Power setups all used brass inverted flare fittings as well, using 3/8" and 5/16" aluminum tubing.




I prefer the OEM look and reliability of the inverted flare fittings, however getting them to work in some close-quarter installations can be a challenge.

 

I think they use the double flare because it is less apt to split.

 

AN lines regularly see 3500 psi on aircraft. AN are all single flare. No need for double flare.

Kevin, I don't follow the question. What would you expect to see on the other end? Another flare fitting? Did I win? I'll take the stuffed toad playing the guitar.......

 

This is correct. A single flare is easy to split both while you are making it and also while you are installing it. Aircraft use AN fittings which are single flare, but ask any aircraft mechanic and he'll tell you how many AN fittings he's either cracked or galled (aluminum) from over-tightening. I've made single flares on brake lines, but double flares are a good insurance policy because you won't be able to tell that your new single flare has split until it's installed and leaking, and at that point it's a pain in the ass to replace.

 

I took Kevens advice plus . The 62 Falcon original pieces and the 68 302 both use straight fittings with 3" pieces of hose clamped rubber hose. Both 93/84 Chevy trucks have inverted flare fittings, the 6 Rochester carbs inverted glare fittings, three Autolite 2100 cards straight hose fittings. two newer holly carbs inverted flare.

Then I found a Parker catalog and each style fitting listed it use and only inverted flare was listed for automotive use, so this morning it is off to Napa. In looking at the fittings it also will look better as they are smaller than the other styles and will sit closer to the carbs.

Thanks for all you input, and hopefully tomorrow the floor in my shop will be dry so I can go back to welding on the 54 F100 project. The floor gets wet each year when the first humid hot day comes and the semiunderground shop floor is cold and and the moisture condenses on it - not the best for using electrical things.

jim h