Fuel lines

[72cudamaan]

Didn't know of a better place to put this sooo, at what point or HP do you consider
going from a 3/8 fuel line to a 1/2" line? Just street use, mechanical fuel pump and 850 carb.

[Chryco Psycho]

I Was able to run 12.0 @ 112 mph on a 5/16 line before I ran out of fuel in a 1/4 mile pass
so I went to 3/8 , if you do the Pi R squard you gain about 20%  flow so you would probably be running 10s to need more than 3/8 line , but you also need a strong fuel pump to push the weight if the fuel forward against the G forces as well

[mach3107]

do you need bigger then 3/8 line for 500hp?

[moparmaniac59]

From what Chryco said, I wouldn't think so, unless you're racing and even then at 500 HP I don't think you'd starve the engine. I run a 3/8" fuel line to a mech fuel pump and a 1,000 cfm carb on a 543 with over 600 HP and I've not encountered a fuel starving problem. 


                                                                             Matt B.

[cudabob496]

I think my electric fuel pressure gauge was under $100. A valuable
tool, and it would certainly tell you if you were having fuel supply problems,
or any other problems, like clogged fuel filter, or fuel pump issues.
Just a small transducer that hooks up to the fuel line right before the carb,
and goes to a nice Auto Meter gauge.

Cheaper than running new fuel line.

[MEK-Dangerfield]

I still have the 5/16" fuel line on my car with a 440. Street use only, but with a hi-volume fuel pump and an 850 CFM carb.

I have an internal fuel pressure gauge, so I can see if it keeps up when I nail it.      No problems.

[cudabob496]

Ya, even if your fuel line could not keep up, you still got two big bowls on fuel on a Holley
you gotta empty first.  Fuel line diameter is only a big concern if you are
WOT for a quarter mile.

[BS CUDA]

Ya, even if your fuel line could not keep up, you still got two big bowls on fuel on a Holley
you gotta empty first.  Fuel line diameter is only a big concern if you are
WOT for a quarter mile.

Yup - I run 1/2" line front to back with a 1/2" sending unit and a 3 line w/ return regulator but I am now being told a larger electric fuel pump is required to keep them full at continued WOT. 1 change always requires at least 2 more    Oh well if I wasn't creating reasons to work on the 'Cuda I'd probably be sleeping or something ridiculous. 

[Chryco Psycho]

1/2 line holds a lot of fuel , you need a GOOD pump just to overcome the G force pushing back to the tank

[cudabob496]

I've got 1/2 fuel line, but it comes out of a fuel cell in the trunk, so no serious concerns about
losing fuel pressure, especially with the fuel cell about 1 foot higher than the gas tank!
Since I don't "officially"race, its all probably overkill for the street.

[brads70]

I have 1/2" supply and return lines. Using a Mallory electric pump, no problems so far.

[cudabob496]

of course, 1/2 inch fuel line is a waste if your sending unit is only 5/16 or 3/8s.
And, the fuel pump and fuel filter may also be causing a restriction, so that
you really don't have full 1/2 inch fuel line flow! Nother good reason for
a fuel pressure guage.

[mach3107]

thanks for the info guys. I think I'm going to buy 3/8 from Inline Tube. I'm using a stock fuel tank with a 3/8 pickup and an electric pump towards the back of the car. And a fuel regulator (with gauge) will be mounted on the inner fender feeding an 850 cfm.

Does anyone have a reason why I should also get a return line?
I was told the factory lines are a bear to put in, is that true?
How dose Inline Tube ship something that long?

 

[Chryco Psycho]

they fold the fuel lines in have with a gentle bend , they are not hard to install , , they clip along the frame , some electric pump require a return line + it keeps the fuel cooler , make sure you replace the pick up as well

[cudabob496]

on my 600+ horse setup, a mechanical fuel pump keeps the pressure at 6 to 7 psi all the time,
for my 850 Holley DP.  No need for a regulator or return line.