I am in the process of replacing the fuel lines in my 79 F250 and was debating whether to go with nylon or stay with steel. I have read numerous posts on various websites and the opinions are mixed.

Has anyone with a Straight 6 used nylon lines? My biggest concern is routing of the fuel line from the pump to carb (heat issue) as well as fittings.

Any suggestions?

 

Go with the steel, Nylon is a fine system, (just finished installing nylon) but it is neither cheap nor the best solution. My donor 88 used all nylon lines, that's what I copied in the transplant. But after scouring the junkyards I've noticed they didn't run all nylon for very long. Most rigs I see changed to steel, with hybrid nylon and braided connections to engine.
Parts support isn't quite there yet for custom/new nylon systems. And after buying the compression tool, that installs the fittings it is spendy. If I had to do it over (which I probably will in the future) I'd install steel lines, with braided stainless steel connections in and out of the main lines.

 

Definitely good to know. Thank you.

What about rubber lines all around? Not trying to be cheap, just curious as to whether it is an option or not.

Also, if i kept the existing steel lines, any recommendations on how to clean them up?

 

I have rubber/emissions fuel line from the mechanical fuel pump to the carb. Had it for years...no problems. I wouldnt do it on a EFI truck, much higher pressure.

 

What about rubber line from tank to fuel pump along the frame? Is that an option or even safe?

 

Rubber deteriorates and with E10 gas it happens even faster.
Use as much steel line as possible.
From the tank, use a short piece of rubber to a steel line along the frame, just have it easy to replace, if necessary.
Also need a rubber flex line from the frame to the fuel pump. These are all suction lines, so at worst they will just drip.
For safety, use a steel line from the fuel pump to the carb, this is the only line under pressure. You really don't want gas spraying under pressure all over a hot engine.

Easiest and cheapest is just to buy brake line, comes flared with fittings, cut one end, bend and reflare. Inverted flare unions are available for properly extending lengths.

I've used rubber lines to the carb before with no problem, but I don't do it any longer, older and hopefully smarter.