[Jacques Reed]

Hi Svenn,

Not familiar with the C15A fuel lines as I am a Ford F15A person but first up never use copper tubing for fuel lines. Flexing will cause copper tubing to get brittle and fracture. The cabin flexes relative to the chassis on the rubber and spring cabin mounts so the fuel line on the chassis will flex between the chassis mounted fuel filter and the fuel valve attached to the cabin floorboard. Eventually it could fail if made of copper.

Assuming Fords and Chev CMP's have some things in common use 1/4" Bundy tubing same as used for hydraulic brake lines.
My Ford F15A fuel lines have double flares and SAE inverted flare fittings on the tank changeover valve. Again, same as used on brake lines. It appears the fitting on your changeover valve may be compression fittings using an "olive" to seal the tube as is often done with copper tubing. May work Ok with steel tubing also, but I prefer double flares.
If it is good enough to seal against hydraulic brake pressures it is good enough to seal against petrol leaks in the fuel lines.

Hope this little snippet is of some use.

Cheers,