The issue that I know of with copper is fatigue from bending. This can happen most when you have a copper line running from the engine to the body or frame. The engine moves independently from everything else. This can be reduced by making coils that take up the movement. After time cracks can appear and then you have a failure. My 1960 Austin Healey Sprite has had copper fuel lines since new and they are still fine. I used copper on my rebuild of my 1940 1/2 ton. Go to my web site and look around on the current progress. I have pictures of my engine with copper fuel, vacumn and water heat for the intake manifold.
