Thread: AN fittings and fuel lines

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Couple thingsto mention. I did a EFI conversion on my '65 Chevy 3/4 ton & learned a few things.

The fuel return line should be one step larger (i.e.: -5 pressure feed, -6 return) than the fuel supply line to prevent any back pressure on the system wich will push more fuel to the injectors than you want under higher loads. Most systems vary the voltage to the pump between ilde & WOT to maintain constant pressure on the manifolds. If there's back pressure this can really mess with your mixture.

It's good that you're using AN fittings, when done properly they wont leak for ages & look great to boot. Where you may have an issue is your pump. Are you using a stock or aftermarket? Many aftermarket pumps can be fitted with AN fittings, this is a good thing to know because if you use steel braided line it can be a bear to get on & off the standard fittings & you may want to go with a std. 80-100 PSI rubber fuel line.

Something else that works great & looks better is using hard line on the longer sections under the car. They can be run up inside rails or along body chanels w/o taking up as much room as hoses would. Also MUCH easier to keep where you put them, only need to mount it avery couple feet instead of every foot. This also works well if you have the stock type pump with nipple fittings as you can run a rubber hose between that & the hardline, then in the engine bay you can use a steel braided line. This is how I did my truck & it looked sharp. Never once leaked after several thousand miles either. (altho I did cheat a bit, I used teflon hose, stainless lines, had my fittings finished at an aviation hydraulics shop & pressure tested to 1,000 PSI, who says overkill is a bad thing? lol).