72 Charger 318 fuel return line and/or fuel vapor line?

[JR_Charger]

Inline Tube has a 5/16" fuel vapor line and a 1/4" fuel return line listed in their catalog. What is this 1/4" fuel return line? I'm sure I only had a fuel line and a vapor line (which appears to be 5/16"). At first I thought the vapor line might be 1/4 for small blocks and 5/16 for big blocks, but that doesn't appear to be the case.

Here's the 1/4" fuel return line - They use the same illustration for the 5/16" fuel vapor line.

Is it 1/4" for Slant Six and 5/16 for V8's?

 

[moparmarks]

440HP and Hemi cars only got a 3/8" supply and a 1/4" return. All others just got a 5/16" supply and no return.
70 with N95 and all 71-up got a 5/16" vapor line.

 

[JR_Charger]

Thanks!

Any idea how much HP the 5/16" supply and 5/16" vapor system will support?

 

[moparmarks]

I've ran my 440 with a Holley 750 WOT through all the gears and never ran out of fuel with a 5/16"

 

[moparmarks]

Probably wouldn't support 600HP.

 

[JR_Charger]

My target is 500HP at most in this car. I'm beginning to doubt I'll get that far.

 

[moparmarks]

I'd run a 3/8 just to be safe.

 

[JR_Charger]

I could switch to 3/8 if it looks like I'm actually going to make real power, but then I've still got the 5/16 vapor line instead of the 1/4 return line.

Does the 1/4 return line go to the gas tank? What about the vapor recovery tank? It sounds like the 440 cars must not have had it.

Rockauto has a Liland Global sending unit (SUDG19) with a 1/2" outlet - what is that about?

 

[Bee1971]

My 1971 Superbee 383/432 is 500 HP

Like Mopar marks said it left the factory with 5/16 fuel line and vapor line

When I was having ignition issues above 4500 Rpm’s I wanted to confirm fuel pressure at the Carter AVS at all Rpms on the road

So I mounted or taped a temporary fuel pressure gauge to the outside windshield basically in front of my face - The hose ran to a T on the OUTLET of the fuel pump right before the carb

A new factory type mechanical fuel pump was on the engine - The fuel pump push rod was the factory installed from 1971

About the only thing I did not replace internally

At idle I was at 6.5 psi

It never dropped below 5 psi throughout all my testing

I also have a video

So I knew I wasn’t having fuel pressure issues with a Carter AVS and Edelbrock AVS2 800
Mechanical fuel pump and factory 5/16" fuel line