MTFCA Forum

I'm getting my Model T ready for a tour in two weeks. The fuel on/off valve on the carb has been sticky so I decided to try to lap the valve and lube it with some EZ Turn. Over the last couple of days it also developed a slow leak at the valve so I decided it couldn't wait.

I removed the valve today and lapped and lubed it without incident. I decided to change the neoprene packing and in looking closer at the end of the line I made a shocking discovery.

I had fabricated my fuel line out of copper-nickel brake line, smart eh? Well, when I looked closely at both ends, this is what I saw (photos.) A failure waiting to happen and something anyone who used similar tubing might want to check out. Why this happened? I have no clue. Vibration I guess. The line had 3300 miles on it.

You need this: https://www.modeltford.com/item/2916.aspx to keep the line from flopping and inducing tension/stress necking at the two attachment points. Choosing a more ductile material such as brass as original or far better, copper, would also be advised as well as providing the support and strain relief it needs.

The material you used is not intended for use where it is unsupported over any large distance, or unsupported with induced vibration.

You're very lucky to have caught this when you did. I know you know that.

I thought copper line was even more susceptible to breaking at the nut from vibration.

They will often break if a compression ferrule is incorrectly substituted for the original felt (or neoprene). The original fitting is not designed for a ferrule and will leak. The leaks lead to further tightening and the nearly certain subsequent fracture of the copper line. A properly installed brass or copper fuel line has little chance of breaking. An improperly installed brass or copper line has a high likelihood of breaking. I've seen plenty of improperly installed lines and they invariably show restrictions due to uncontrolled ferrule squeeze and often the start of stress fractures around the ferrule.

It is one of the first things I look for on a car sent in for service and in nearly every case, if the car belongs to a casual hobbyist who is only rudimentarily acquainted with mechanics, the fuel line is done wrong.

In addition to what Scott said, copper is fine if you use thick walled copper line. The stuff used to bring water to your refrigerator is thin walled. Make sure you use thick wall.

Thanks for clearing things up guys

I should point out that I used neoprene feed pipe gaskets, not a compression ferrule. The Gas Feed Pipe Clamp that Scott mentioned is for a later year car than mine but I've ordered one because it looks like a smart idea. I tried to route the line correctly when I installed it and have never put a wrench on the nut fittings since installation until yesterday. I posted my photos hoping someone else would benefit from my experience. I have to tell you that I was surprised by the degree of deformation.

This is really interesting, Tim. I'm assuming that the necked down areas were directly under the gasket at both ends ?

The copper-nickel tubing seems to be very successful for brake lines, so the only reasonable explanation has to be vibration, however small. This is a real warning for anyone contemplating use of the material regardless of where it's employed.

I got bitten by the copper line fatigue issue many years ago and have tried to avoid copper wherever possible. But I do like the copper for originality. On my latest (airplane) project I went so far as to make new fuel lines out of steel brake line material, then had them all copper plated for appearance. It wasn't cheap, but I feel a whole lot safer that way.

Dick

Dick

when used as brake line, the line is typically clipped firmly to a structural member every 18-20 inches and has no way to be energized by anything other than very high frequency vibration that is not going to occur in an automobile. This is a very different environment than when used unsupported for a significant length such as a T. Add to that the requisite horizontal bend(s) in the fuel line and you have also introduced a twisting element with a small moment arm. Introduce tension and vibration and what you might expect is exactly what Tim encountered. This is why I think the addition of a clip to the frame mid-point of the line is a good idea and it appears that Ford thought so, too. For a man obsessed with reducing an assembly by a single screw to save costs (in volumes of millions of parts), I'm sure the addition of this clip was not done lightly and is born of fuel line failures, not a few of which were likely catastrophic.

While nickel/copper alloy has a higher fatigue strength (nearly 2:1) to copper, I am betting that the brake line ID is a good deal larger than heavy-wall copper tube and ultimately, resistance to damage in a T application is not nearly as high as one would expect (as Tim is showing). And as mentioned above, it is definitely the heavy-wall copper tube you want...not the flimsy Lowes/Home Depot stuff.

Scott_Conger wrote: ↑

Sun May 16, 2021 8:44 pm

They will often break if a compression ferrule is incorrectly substituted for the original felt (or neoprene). The original fitting is not designed for a ferrule and will leak. The leaks lead to further tightening and the nearly certain subsequent fracture of the copper line. A properly installed brass or copper fuel line has little chance of breaking. An improperly installed brass or copper line has a high likelihood of breaking. I've seen plenty of improperly installed lines and they invariably show restrictions due to uncontrolled ferrule squeeze and often the start of stress fractures around the ferrule.

It is one of the first things I look for on a car sent in for service and in nearly every case, if the car belongs to a casual hobbyist who is only rudimentarily acquainted with mechanics, the fuel line is done wrong.

Thanks Scott, this explains a lot. I have heard many T folks swear that steel was the only way to go and that the other way would lead to disaster. Others swear that steel will give trouble. I actually removed a copper line I had recently fitted out of fear it would break. The new steel line works fine so far.

As long as we use the thick walled tubing & the Ford style fittings & felt or modern neoprene packings copper, brass or steel will all work?

Dick, the necked down area on the carb end was invisible until the nut was backed off. If it was visible when I turned the fuel on and off I would have attended to it long ago. As it is, anyone using lines made of softer metal needs to be alert to the possibility and all should consider supporting the line as Scott suggests.

I'm just glad I found it before it failed.

Paul you should be fine. Support either, if possible

All: Do not overtighten the pack nut when using neoprene or felt (particularly neoprene). The neoprene needs to only be "tweeked" tight. It is an energized rubber in this application and tremendous compressive pressures can be had if you horse it down. The felt does need to be tightened a little more due to it's composition. A good smear with some softened bar soap on the felt, before hand, will provide a good seal if you've experienced weeps in the past using felt and were unhappy with the results.

Scott - sooo.... it it's just tight enough that it isn't leaking that's enough?

Comment: It is always a good day when you learn something new....thanks all!

I believe original fuel lines were tinned brass, not copper. As mentioned elsewhere, none of the original carburetors or sediment bulbs are machined to seal against a brass ferule. They are as cast, and a ferule will never seal unless deforming force is used. Scott's advice to tighten the packnuts just enough to stop weeping is the way to go. Then you have more up your sleeve if it does weep a little later on to make a new adjustment.
I was interested to read of a clip/clamp used on the line. I have never come across same. What form did it take and where was it installed?

Allan from down under.

I've attached another photograph that you might find interesting. The end of the Copper-Nickel tube in the carburetor is simply necked-down in the area of the nut while the end that was in the gascolator is actually dished inwards. What's funny is that the car ran just fine, even with a restricted fuel line. Steel lines for me!

Ivory soap, if you're a traditionalist. These kids today are using pink Zote. Either will serve, just stay away from that scented stuff in the fancy wrapper.