Fuel Line Replacement

[Chuck Griffin]

Anyone know what size fuel line was used on a 40 Buick super? I need to replace the entire line from the tank to the fuel pump. I was thinking of using the steel braided ptfe line. Your thoughts?

[Bloo]

It was almost certainly 5/16" steel "Bundyflex" brake tubing, using double flare fittings. Cunifer might be a good substitute if you are concerned about rust. I wouldn't really recommend flexible line for the whole run, just a short piece of high quality flexible line to absorb engine vibration at the fuel pump end. I would probably use 30R9 rubber fuel injection hose there. If there is a hose at the tank end, I would do the same. While the tank is down, I would add a ground wire from one of the sending unit mounting screws over to the frame to prevent fuel gauge trouble.

[Buick35]

I've always just used copper tubing,it seems to work well and easy to bend.

[buick looks fine for 39]

An excellent product I've used in the past is a 5/16 fuel line stock produced by Thermoid. It comes in 25 foot rolls and has a rust resistant copper/nickel plating. It bends easily and once the line is bent into the desired shape the fuel line work hardens during the bending process. The only problem I had was a forming a tight bend near the gas line where it was double flared. It seemed that double flaring the end of the gas line work hardened the metal and I kinked the gas line when I tried to make a tight  bend close to the double flare. Be careful attempting to make the gas line too pretty by eliminating seemly unnecessary sloppy bends in the line. The extra bends and length especially in the engine compartment allow the line to safely move when the engine is torqued under acceleration. Also an electric fuel pump is not a bad idea and it works best when it's placed close as possible to the gas tank. Be careful with copper tubing; over time it will work harden and form stress cracks which can be catastrophic. 

                                                                                            Thanks

                                                                                                Leif

[Buick35]

Good to know,I've had the copper tubing on my Buick for about fourty years now and it's still good but I'll keep an eye on it.Thanks.

[Bloo]

I have an teens car with it too. It was common in those early days. Not so much by 1940. It's fine until one day it isn't. Then it leaks or falls off. I can't imagine why anyone would use copper today when cunifer is available. Cunifer looks like copper, bends like copper, and does not work harden. Buick would have used Steel Bundyflex for the run to the front, but may have still used copper for the fuel pickup in the tank.

 

Work hardening and cracking from vibration is a known property of copper. You can't fool mother nature.

[Matt Harwood]

+1 for Cunifer. Incredibly easy to work with, done once and you never have to touch it again.

 

Do not use flex hose for the entire fuel system. That's just hack work.

[Ben Bruce aka First Born]

3 hours ago, Matt Harwood said:

 

 

Do not use flex hose for the entire fuel system. That's just hack work.

 

 Some hacks are effective! 😁

 

  Ben