Fuel line question

[jonny0666]

I have a 71 RR factory 440 car. I currently have a 400 that I am putting in it for now with the intention of eventually putting a 440 back in it. I am replacing the old 3/8” fuel line with new 3/8”. Would that cause a fuel issue with the 400? For the 400 do I need a fuel return line because I’m running a 3/8” fuel line? And do I need a vapor return line? Thanks in advance.

 

[snakeoil24]

return line always makes for a big improvement

 

[HEMI-ITIS]

No,no,no and no.

 

[snakeoil24]

Why?

 

[WileERobby]

What is the 5th digit of your VIN ? The only 440 in a 71 RR is a 6 bbl.

 

[HEMI-ITIS]

Vapor return line was for emission control.Unless your trying to be OEM correct,if not IMHO none of that is needed.

 

[72RoadrunnerGTX]

Vapor return line was for emission control.Unless your trying to be OEM correct,if not IMHO none of that is needed.

The evaporative emissions system specifically and is part of the original fuel tank venting in ’71. A functional evaporative emission system will not have any adverse effects to performance. No reason not to restore the original design. For a ’71 v-code car, if that’s what it is, there would have been a 3/8” fuel line, ¼” return. And a 5/16” vapor line to the fuel tank vapor separator in the left rear wheel well.

 

[vance.dykes]

The evaporative emissions system specifically and is part of the original fuel tank venting in ’71. A functional evaporative emission system will not have any adverse effects to performance. No reason not to restore the original design. For a ’71 v-code car, if that’s what it is, there would have been a 3/8” fuel line, ¼” return. And a 5/16” vapor line to the fuel tank vapor separator in the left rear wheel well.

if you want to less possible fuel system problems replace all the lines. that way its very hard to get vapor lock so you will cruise and not be waiting on a tow truck. it is cheaper to do it right the first time than to fix it on my way to dinner.

 

[Triple Black 73]

The feed line gets connected to the fuel pump with a rubber hose, thus the engine size doesn't matter. I highly recommend getting a return line because it will keep your fuel cooler and more consistent fuel pressure at the carb.

What does matter is the factory style hard line from the pump to the carb. Those line are engine and carb specific. I didn't get the right line. It worked, but it was a bugger to install and truly never fit right.

I now have -6an feed & return lines to an Holley Sniper EFI.

 

[jonny0666]

Awesome thanks for the advise and feed back. I’ll let yous know how it turns out.

 

[biomedtechguy]

Vapor return line was for emission control.Unless your trying to be OEM correct,if not IMHO none of that is needed.

If I may jump in,
Last late September I replaced the stock fuel pump with a Carter M6903 mech fuel pump. 120 gph (appx double the stock pump rate), "stock" fuel pressure (4-6 lbs). Works great.
My question is when I did that I installed the Promax AN -6 lower braided fuel line and the Promax 6 bbl upper fuel lines.
This left me with no evident way to reintroduce the new fuel vapor separator (I had just bought from Mancini) to replace the old one. It has the 3/8 hard line (Hemi and 6bbl cars, mine is a V-code) from the fuel tank to a WIX 3/8 inline fuel filter, then the fuel pump, and an inline reusable 40 micron metal fuel filter right before the pressure gauge, then the 3 way lines. The 40 micron inline reusable fuel filter is incorporated into the carb end of the lower fuel line from Promax.
I just plugged the return line.
Any reason to try to reincorporate the vapor separator?
Thanks.