Fuel line/hose connection

[BAO B]

Hello,
I'm in the middle of complete over hauling the fuel line in my car.
I read from an article suggesting that the fuel line (aluminum) should be double flare for leak free connection. From what i've seen from the original porsche fuel line, none of the fuel line end is flared... As pictured, this is what i'm working with (without flaring) on my new line.
Is this good enough with a good clamp around the rubber hose and the fuel line?
Should i be concern about leakage any time soon?
Or should I flared all the end of the fuel line... ? which i hate to do.

Thanks,
Bao

[Flat6pac]

I would seal with avation Permatex to make sure there is no leaks.
Where is that piece youre working with located?
Bruce

[Porboynz]

If thats the tunnel fuel line then the factory did not flare the ends and neither did I when I replaced the line. Make sure the flexible hose you connect to it is correctly sized and slips on with medium force (not loose) then make sure you use a fuel line hose clamp. The clamp in your picture will damage the rubber, you need the clamping type with the smooth inside surface. I figure the fuel in these lines is not pressurised so I did not bother with sealant or flares. So far so good.

[BAO B]

Bruce,
I use a. permatex on most gaskets sealant, but never on fuel hose/line.. where do you put the sealant.. on the fuel line and just slide the fuel hose over and clamped it?
These connections are from the fuel tank to the front firewall and coming out from the rear firewall going to the engine.
Thanks, Bao

[BAO B]

Porboynz,

Correct, the factory line has no flare at the ends. The rubber hose fit tight, but not overly tight. I will use smooth inside clamp for the rubber (only) hose..good point.
How long ago you replaced your line? Any problem with leakage?

Thanks, bao

[BoxsterGT]

In most cases, even the early 911s used a hose connection like this with a bump to keep the hose in place................



With carbs and fuel pressures less than 10psi a simple Norma type hose clamp is adequate. (I think the one shown does not have perforations and is the correct type.)

However, later cars using fuel injection have operating pressures that are much higher (30 psi & up), to the extent that simple slip connections & hose clamps are inadequate & dangerous.

To the best of my knowledge, Porsche never used aluminum tubing down the tunnel. Steel & plastic tubes yes, but never aluminum. What you have is aftermarket, and that is fine. Our host offers SS tube which is even a better choice. However, a proper fitting at each end is absolutely necessary unless you are running only 5-7psi w Carbs.

Its a simple matter to form a flare on each end with a proper matching hose fitting..........



Then, if you ever want to run fuel injection and you change to a hi-pressure fuel pump you dont have to go back in to do it properly the 2nd time around.

I have lots of the correct Metric fuel fittings and would be glad to help if needed.

Just my 2 cents........

Len

[Porboynz]

We may be getting our hoses mixed up here, the 2 x fuel lines that run through the tunnel do not carry pressurised fuel on my MFI car with the fuel pump at the rear. The feed and return are both are at gas tank pressure whatever that might be with a full tank. All the hoses on the pressure side of the fuel pump and MFI/fuel filter housing have "spear" fittings as standard. I had to replace the metal feed fuel line through the tunnel after I very stupidly ran a taper tap down into the seat mount holes and punctured the line, twice. I replaced an otherwise perfectly sound 40 year old factory fuel line with soft drawn metal fuel line from a speed shop, looks like aluminised/ plated steel to me. I have had no issues with fuel leakage. I pushed the replacement fuel line in from the engine end and rather than buy a tubing bender and drop the front suspension to use it to angle the fuel line away from the front suspension I used a brass right angle fitting at the front . (normal brass fitting with brass ferrules that slip over the pipe.) IMO if the factory did not bother with flares then neither will I, but if you want to be 100% certain it would not hurt either to put a small flare at each end of these tunnel lines. Some 911's have a fuel pump at the front and I agree it would be sensible to have flares wherever the fuel is pressurised, to stop the pressure from forcing the rubber hose off the metal line.