I'm replacing my fuel line with 3/8 steel. Do I need to flare the ends before slipping on the rubber tubing, or does this just accelerate wear on the tubing?

not needed unless running a lot of pressure where you run the risk of blowing the line off.

My thinking was to slide the line extra-far with a little oil, then double clamp it. I would think that with the added vibration of a 4x4 that the raised edge on the tube would cause early hose failure. No one wants early hose failure.

Or you could flare w nuts and add barbed ends, nice to have it plumbed for EFI in advance.

Thought about that as well. Ive only got a single flare tool and want to get it done quick 'n' dirty for next weekend. Those need to be double flared, right?

That I don't know, I've only ran the lines on Willem's truck but haven't flared them yet. A double flare is easier on bigger lines, and the tool is cheap.

I've gota double flare tool if you need it... I would flare and barb, just to be ready in the future. Car quest down on Alameda should have the fittings you need, just walk in back and look for yourself, so you know what your getting

I made my steel fuel lines when I installed my Holly Pro-craption stuff 15+ years ago. I flared all the lines with a cheapo flaring tool. I worried about cutting through the rubber lines too. In 15 years I've never had a line cut through, or even show signs. I'm using the same main line still now with my EFI, single clamped, no problems.

i would double flare and barb as well.. allows for EFI pressures and you can change things out pretty quickly