Question on fuel line OD?

jjbubaboy

I am going to re plumb my fuel line from tank to carb and add a return line per Walt's tech tips on my 36T.
What would be the best OD size tubing to use, 3/16, 1/4, or 5/16? And why?
Also will compression fittings where needed be OK, and is their any difference in availability based on tubing size? (OD)
Any input always welcome!
Thanks,
Jeff

[Deleted User]

The line to the fuel pump and carb should be 5/16. The return line should be 1/4. Electric pump should be right at the gas tank with a see through filter in front of the electric pump, and then a filter before the engine pump and the 3 outlet filter before the carb is where the return line starts. Should have all pipe fittings knurled with the correct pipe fitting. Stay away from copper or brass tubing, use steel or stainless. The return line can be neoprene gas line, as there is no pressure here. Just make sure you have the check valve in return line. Walt.

jjbubaboy

walts garage-53 wrote:

The line to the fuel pump and carb should be 5/16. The return line should be 1/4. Electric pump should be right at the gas tank with a see through filter in front of the electric pump, and then a filter before the engine pump and the 3 outlet filter before the carb is where the return line starts. Should have all pipe fittings knurled with the correct pipe fitting. Stay away from copper or brass tubing, use steel or stainless. The return line can be neoprene gas line, as there is no pressure here. Just make sure you have the check valve in return line. Walt.

Hey Walt,
I already have the pump and filter back there. What do you mean 'pipe fittings knurled with the correct pipe fitting'?
I was going to use aluminum fuel line for travel both ways. Wont their be pressure in the return when the electric pump is on?
Any by check valve do you mean a one way pressure valve?
Thanks!
Jeff

[Deleted User]

I'm sure Walt will agree Do Not Use Alum. on a fuel line. Too Soft - Too Brittle, And don't use compression fitting's they work loose from movement, use flared fittings -double flarred if you have the right tool,
Roger

GrimGreaser

Swagelok (A-Lok, Yor-Lok ect...) type compression fittings should work great. Tighten them right and they'll be trouble free. I trust my life with these type of fittings at work everyday, and any flare tool I've used (that I can afford, mind you) has been a worthless POS.

[Deleted User]

Do not, repeat, do not use aluminum line to the engine. It will crack and when gas goes 15 percent alkie, it will eat the aluminum. Just flare the ends and use the correct fittings. The return line can be 1/4 neoprene gas hose, and by the word, backpressure, you must have a sitting in the return line with a 30 or 40 thousand hole to slow the flow, or else going up a steep grade you will starve engine. Walt.

jjbubaboy

OK, aluminum is OUT!
Any suggestions on who sells the steel in 10-20 or so feet lengths? The only reason I was looking at aluminum was I found it in the Summitt Racing catalogue and it was priced reasonably and listed as fuel line.
Jeff

[Deleted User]

I know Kanter & JC Whitney each sell fuel and brake line kits,
Roger

hudsonguy

Jeff,

Here's a picture of the restriction Walt is talking about. This effectively slows the return lines flow to just a trickle, which is all you really need to avoid vapor lock. Like Walt said, this is so you won't starve for fuel on long uphill drives, etc. This is not a pressurized line, the return line just takes the excess fuel that the carb doesn't want (or need) and flows it back to the tank.

Here's where I bought mine;
Barb Fittings; http://www.mcmaster.com/#5346k42/=b6qr5i
Orifice: http://www.mcmaster.com/#2712t434/=b6qrho

When I installed mine, I just used 1/4" steel brake line for the return line (in long lengths connected together) which is readily available at any parts store. I used stainless steel 5/16" line for the tank to engine line, with all of the fuel filters that Walt spoke of. The SS lines are next to impossible to flare, so if you're doing this yourself with less than a top of the line flaring tool, you probably want to just stick with steel line.

This set up has worked flawlessly for me since I installed it. Good Luck, Doug

[Deleted User]

Does anyone know how many feet of line are needed to complete the supply side and how many feet are needed for the return side?
Wouldnt the stepdowns use two diffent lengths? (long and short wheelbase)

And how about the 47 coupe supply and return? Thanks Bob

[Deleted User]

What I've noticed in repairing Hudson brake lines was they would use standard off the shelf lengths. And put a bend in it to shorten it a little if needed. I found this on my 51 super 6 . Every bad drake line I replaced was a standard length. And it was an original untouched car. I would assume the same thing would make sense with the fuel lines as mentioned in the previous post's.
Roger