The Stovebolt Site Forums The Shop Area Engine Shop Copper gas line

So today I drove the 53 to the dump, filled it up on the way. It has a new tank, I have been wrestling with getting the new gas line good and sealed. The replacement tank (original form from LMC) had a different outlet hole from the original and it has been a hassle finding a good connection at the tank. The worst is that even when everything seems to be tight, it is first when the tank is in place that the Leak makes itself known. And the leak is at the bottom of the tank, impossible to tighten when in place or even to inspect. I have had the tank out three times trying to test that outlet connection before re-installing.
Today it started to leak again. From the bottom of the tank. (above the floor of the cab but behind the seat supports). I had first placed the tank on sawhorses, hooked up all lines, filled up with a coupla gallons of gas to see that all was tight, but once it is on the road and all filled up it leaks again.
The old tank had a threaded tube about 4 inched long screwed into the tank, extending through the floor to the petcock valve, from there to the gas pump via a steel gas line with flared ends. The new tank asks for a flared end from the tank itself. So I used a short piece of old steel line, bubble flared on two ends - one end goes onto the tank and the other into the petcock. I fear I have torqued so hard on the various fittings of the petcock that I have caused a minimal crack on the fitting from the tank which leaks first when the tank is well-filled.
Also, I was recommended locally to use copper gas line. Any of you have experience with this stuff. I am not pleased with my efforts to flare copper.
But that is not the cause of the main leak, I don't know what I will do about that. Why can't an original replacement tank have the same outlet hole that the original had?
Anyone notice yet? This is a rant.
Karl

I believe that copper is generally a single flare. Not really the best thing for fuel, I would think.

Your trouble might be because of using a bubble flare instead of a double flare? Are you sure that the tank fitting is a flare, and not pipe thread?

You ask the hard questions, Dave. The copper seemed unhappy to take anything but a singel flare. And before I answer those other questions I believe I will google bubble flare, double flare, and pipe thread.

I agree that the aftermarket tanks should have identical outlet connections (1/8" FNPT) which are pretty easy to get sealed. You're saying that the tank has a male flare outlet?
I'd be sure where the actual leak is (if it's at the tank fitting from the supplier, you're pretty much hosed, although maybe a crack could be soldered closed, which can be dangerous without safeing the tank). Copper should use a single flare as Dave said, and should seal up pretty well on a standard flare fitting. It's used for stuff like fuel oil, etc.
I'd install a short stub of copper and transition to a compression style fitting (with nut and ferrule) below the floor to work similar to the original pipe nipple. Or you could even sweat a male NPT fitting on the lower end of the copper for the original style shutoff valve.

on edit: if you're having trouble with getting a flare fitting sealed up, a little bit of pipe dope on the flare helps.

Years ago I had a similar problem and I applied liquid gasket sealer (Aviation type from Permatex) to both parts, let it dry an hour or so and then never had any trouble with it. I've also used this same gasket sealer on plumbing connections (water, of course) with equal success.

You don't want to use a bubble flare (which is essentially 3/4 of a double flare). I'm not sure what king of fitting you'd use a bubble flare for, although I did do that (upset the ends) of a tranny cooler line when I installed an inline filter to keep the hoses from slipping off. Either a single flare or double flare should work for copper. If you're getting cracking attempting to double flares, you can anneal the copper half way thru the process, but again a single flare should work fine for copper.

Copper work-hardens very quickly, and becomes brittle from the flare operation. In theory (!) heating it red hot, then doing the 2nd flare should be better.
I prefer a compression fitting if there's a way to do that.

I have read reports that some of the aftermarket overseas tank come with metric threads on the bottom


Ive used spectra brand tanks, came with the correct threads on the bottom.

Annealing copper works. I've done it (not necessarily for a double flare).
But I'm with you on using a compression fitting instead of a flare. Much more dependable.

The replacement tank from China on my ‘62 was metric on the sending unit.

Try Ni-Copp for the fuel lines. Bends and forms easily. Double flare with no problems. Uses standard fuel line fittings.

So here is the latest. I took the whole system out again, tank and lines. My short steel line from the tank downwards has each end with a rather well done double flare, if I do say so myself. Still the upper fitting was leaking. You can see on the first picture the stain from above the cab floor. The ends of the copper line have good single flares. My memory is that I annealed the copper before flaring, but now with everything removed again I annealed the flared ends again hoping that will allow a better fit.
Anyway, with the tank out and resting in its proper position in the free, I reattached the outlet tube with a sealed end, then filled the tank about a quarter to check for leaks. I have already done this once before, found no leaks, than installed it all only for the leak to reappear at the bottom of the tank.
So the tank did not leak, again, out in the free. Then, after emptying the tank,I reinstalled the short tube with a blue gasket cement on the fittings. The tank went back into the cab, the petcock went back into place with the blue gunk on the fittings, and finally the copper line went back in.
Admire the pictures.
The tank has a few gallons back in it now and no leaks yet, but I haven't started it yet. Because of an unoriginal original tank, it has taken about a year to get the new tank into place and a whole sack of frustration.
Karl

Looks good Karl but, isn't there always a butt LOL., from the pic it looks like your using a rigid copper line to connect to the frame line when you should be using a short rubber line from the cutoff valve to the frame inorder to give better flex and not stress the fuel line.
Theres actually a factory reproduction line available: flexible fuel line from most all suppliers.
I just replaced the tank in my 49 GMC and I used barbed fittings and clamped a short piece of fuel line to provide connection between the cutoff valve and frame line.
Good luck
Dave

Using a nipple right off the tank will eleminate those double flairs.

You do need the hose mentioned above due to the cab flexing while driving



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Hi there, Dad! I have that "nipple" lying on the bench and I would have gladly used it. But the source of my problem was that the new "original" tank was not threaded to accept the original setup as seen in your second picture. I am sure both of you are right about the advantage of a flexible hose along the gas line. The original setup which I removed had no flex hose - it was a continuous steel line from the tank to the gas pump, anchored all along the frame. For the meantime the copper line is tight, and there is a lot more flex in the copper than there was in the steel line. Until it starts leaking again I'll run it like it is, it is tight today. If it starts leaking tomorrow I'll chop that copper line.

You will develop a leak in the copper line over time due to metal fatigue. Copper is not as resilient to repetitious bending as steel is.
You need a rubber hose in there somewhere between the tank and the frame.
Carl

Put a piece of rubber hose in as already suggested. I wouldn't run copper myself, I would use steel lines. Copper breaks too easily with just a little flexing.

Yo............copper is for water. In that size, for an ice maker in your fridge.

Well, the choice of copper is just one more example of how common materials in the states (steel fuel lines) are not readily available over here, while seemingly well informed folks at the FLAPs here recommend something like copper that just isn't quite right.
But to be clear, the worst of my problems has been the unoriginal outlet on the NOS gas tank.
Of course, I will be inserting that section of rubber hose toot sweet.
Karl

Not going to give advice on your leak, don't know; HOWEVER:

In the USA, at various eras in the history of the automobile, metal fuel lines have been used on PRODUCTION cars, trucks, and tractors constructed from (in alphabetic order) aluminum, brass, copper, and steel.

Copper was still being used on PRODUCTION performance carbs built by Oldsmobile as late as 1966.

Copper, per se, is NOT your problem.

In the FWIW category, I started playing with cars in 1959, tractors earlier. To date, have had one metal fuel line failure - steel. And several rubber hose lines have failed.

Jon.

1. You can't get away without rubber.
2. One failure of steel in almost 60 years actually proves the reliability of steel. The one failure would have to be analyzed to see if is was steel fatigue, corrosion, embrittlement or a cause unrelated to the material.

Rubber handles vibration, steel or copper not so much.
I agree with bartamos on #1, but copper is OK as well as steel as long as you install a rubber hose to handle the vibration.

Can you rethread one end of the nipple the size that is on the tank?

The threaded outlet from the tank seems to be the same size as the nut on the end of a flared fuel line end, the same as would fit into the outlet side of the petcock. An adapter that would allow the use of the nipple would be pretty flimsy. I am sure it exists somewhere but I wouldn't know how to start looking from where I am. After the latest installation all of those potential leak points are tight, except possibly for where the line goes into the fuel pump. The connections around the petcock have never been a problem, the leak has been from the threaded hole on the bottom of the tank.
The fact is that the threaded hole on the old original tank is not at all the same as on the replacement "original" tank. I cannot be the only bolter who has bought such a tank - in this case from LMC who I consider a quality supplier but the same tank is probably sold by others - and I am surprised that it seems that no other bolter has chimed in after dealing with this situation. The copper line is its own subject but that copper line is not causing my current problems. I would much rather have used a steel line, with or without preformed flares, but I would have to order such a line from the states and that process even for relatively cheap parts is extremely cumbersome and expensive.
So instead I am trying to deal with my problems as farmers have done throughout many centuries, using the available materials to do the best job I can.

I have appreciated all the comments, thank guys! All the mistakes I am making are transforming me into a wiser wrencher. We are all beating a dead horse at this point, the line is not leaking.

The gas tank issue has been discussed before

The overseas tanks had issues with filler neck not lining up and odd ball threads on the bottom

Spectra brand GM55A is made in Canada and is a perfect fit

Availiabe at rockauto.com and amazon for about $180.00

Info might help the next guy

(1) Actually you can get away without rubber. The copper was formed to have a "vibration loop" in the old days, and it worked well. Of course, not as many miles were driven. Rubber is more practical today than the vibration loop, but rubber is the weak link in the system (except for the folks that use clear plastic).
(2) In the same time period, ZERO failures from either copper or aluminum (I have a lot of aluminum lines, as well as some copper). Have never used brass. The factory steel line broke at a flare. Again, simply pointing out that the copper and aluminum are reliable.

Jon.

Jon, point well taken, your experience is respected and valuable.

To beat the horse and to help others in the future who choose to use the search feature. (the next guy) DADS50 is absolutely correct. Spectra is the best and others are not.


Spectra Premium are the best tanks. ALSO, some aftermarket tanks have metric threads! BEWARE. This tank has 1/8" NPT (National Pipe Thread) pipe threads which are correct. There was a little spec sheet that came with it saying it is good for use with up to E20 fuel and biodiesel 5% I believe. This tank is made in Canada. They are very, very nice and many, many guys on stovebolt.com recommend them highly. I was floored by the quality. You won't be disappointed. Mine fit perfectly! 1954 is siphon feed from the fuel tank. 1949 - 1953 were all gravity feed from the tank. All these tanks have a threaded fitting at the bottom. These trucks come with a pipe plug in the bottom for 1954 and 1955. Remove the plug if you really want a gravity feed fuel system. Chevrolet updated it in 1954 since gravity feed is dangerous because if the fuel line breaks for any reason, such as in an accident, the entire tank of fuel will drain. If you're interested in converting to 1954 style, get the later fuel sender and bend up a new fuel line.

Why maintain this crazy petcock valve, leaky, dangerous old style plumbing? It's so easy to swap over. Too many post reveal this is an unnecessary problem magnet. This is an area where originality is unseen and ridiculous.

The LMC tank note "A" advises that tank is for either plumbing system. If there are actually two holes in the bottom, I do not see the reason for this. One hole for either a fitting or a plug would seem to make more sense. At any rate, it does seem that a user of an LMC tank could either switch to top outlet or use the plug hole as the bottom outlet and plug the other funky fitting. (may require a new hole in cab). Spectra tank has one 1/8 NPT hole.