Carbeurator fuel line return direction

[BackfiringDatsun]

Which way does the fuel come in when you have a fuel return line to the tank? Does the fuel come in from the front of the rail and return to the tank out of the back by the valve? Or does it come in at the back carb and return to the tank through the front of the fuel rail?

I figured it came in from the front, except the fuel line size from the fuel filter sure seems to match up with the back which is a 3/8 nipple as opposed to the front with is a 1/4 line nipple (I'm estimating the sizes).

I know most of you probably aren't running fuel return lines, but any insights would be highly appreciated.

I've got a 68 1600 with smog (California car) that I'm putting back together, when I bought it it came in a lot of pieces.

[david premo]

Post a picture of where the two fuel lines meet, the larger line should be the return line, as it’s not driven by pressure. Think of it like the kitchen sink, water comes out of the tap but drain is much larger as it’s not under pressure.
Dave

[redroadster]

The return system is also a fuel warmer ,helps in this weather. Colder gas doesn't aireate as much