If the for what its worth category regarding stainless steel fuel lines:
We have been bending fuel lines for factory multiple carburetor setups for years. Some 20 years ago, we discussed making lines from stainless steel, and contacted one of the large stainless manufacturers. We were granted an interview with their engineering department. The engineers stated quite positively that this MIGHT be a very bad idea. According to the engineers, stainless flares should NEVER be bent more than 37 degrees. Automotive fuel fittings are 45 degrees. The chief engineer suggested that if we were going to make lines from stainless, that we should also make 37 degree fittings to use with the lines. We decided NOT to fabricate any lines from stainless.
I realize others are using stainless, however the above is the "skinny" from someone (the chief engineer, not me) who should know.
In 40 plus years of working on fuel systems, I have seen only one failure of a copper line. This occured at the flare (cracked). Subsequent inspection determined that the flare retaining nut had been cross-threaded at one time in its life, which damaged the flare.
However, for "hot rod" applications, we use either steel or aluminum at the customers discretion. We use copper for the Oldsmobile J-2 tripower as that was original, and have had zero problems.
Jon.
