I don't believe a copper fuel line secured to a frame rail will ever produce a problem. Have them in two old Fords. Also have 1/4 copper brake lines on the gear legs of a Cessna 140 for 38 years. Lots of vibration there. Remember seeing copper lines on refrigeration units years ago. Yes I'm an old duffer.
Perhaps you should also wonder why the automobile manufacturers do not today nor did they in the past use copper for fuel lines, especially in Ford's case where the copper-plated double-wall Bundy steel tubing was used at an obvious cost penalty.
Hmmm.
I have been around fords MOST OF MY LIFE and have never heard ofYour friend is misinformed. Please re-read my note. In the era and likely still today double-walled wrapped copper-plated Bundy tubing costs more than copper tubing. That's a copper-plated sheet of steel wrapped around itself twice, i.e. two separate walls of steel fused together by the copper plating in a unique welding process which gives greater strength and the same level of corrosion protection than any pure or alloy single wall copper tubing.
Actually, compression fittings & flares had been around for MANY years prior to WWII.I love this kind of Ford Barn discussion. Every opinion under the sun! Heres my tuppenyworth (is that more or less than 2cents?) I don't believe any design engineer specified pure copper for brake line. If it looks like copper its probably one of the copper/nickel seamless tube materials that is great for brake lines.
The question was re copper for fuel line. I come from pre-war cars which all had them because that's all they had. We use solder fittings which work well, and anyway, flares and compression fittings wernt invented then.
So when I replaced my rotten '32 Tudors fuel line with copper it was because I had a bunch in stock. The fact that the last 18 inches before the fuel pump are braided synthetic hose, pushed onto the copper and hose-clipped, means it is not period correct and I should probably have my botty smacked
Cheers, Tom.