Any experiences with smaller return fuel line? Pump selection?

[First Bird]

Anyone running a return line smaller than the supply?
Any suggestions for my setup?

Changing directions on my 1968 Firebird build (car not running yet):
On the car now: 1/2-inch RobbMc pickup, 3/8-inch steel line, Carter Street Mech Pump, Quadrajet



New plan: 1/2-inch pickup, Mallory 4140 Electric Pump, 1/2-inch aluminum supply, Mallory 4309 Bypass Regulator near carb, 3/8-inch steel return line, Quadrajet

I hate to rip out the nice shiny new stainless 3/8-inch tank-to-pump line, so I'm going to run it and change it out if there is a problem with excessive backpressure in the return line. I know this breaks the rules about return lines being as large or larger than supply. Can someone tell me it's going to work out fine? (laughing)

Engine specs. 455, KRE Heads unported, Crower cam 230 .520", 10.2:1 CR, headers, Quadrajet
Will drive this car. Will see some track time - the kind with curves, not quarter mile.

[Johnny Blaze]

Most recommend against it, though my factory EFI return line is smaller than the feed line.

[Randy67]

Most factory cars seem to have smaller return lines. I didn't have any issues with the LT1 swap I did, used 3/8 feed and 5/16 return which matched the factory sizes. I would run the 3/8 and see if you have any issues, then change it then.

[bbcc]

I'm rocking a 1/2" feed with 3/8" return on my truck. No issues at all. Pressure is rock solid, and the fuel is nice and chilly. The big thing is to make sure there are no tight bends that will reduce the cross section. Also, try and keep the bends <90 degrees to minimize head loss.

[Johnny Blaze]

According to Aeromotive, a smaller return line will cause a creeping rise in fuel pressure.

[First Bird]

Thanks for the replies everyone. I am going with the 3/8 return and see what happens. Will fix a problem when there is one.

[First Bird]

Here's how it worked out. Fine. Back pressure at the regulator is 1.5 psi. That's with the regulator totally closed so it returns all fuel to the tank. Mallory says anything under 3psi is OK.

[sam 74]

i use -8 from tank and 3/8 return with no problems going on 10 yrs now.

[esenior]

I'm running a -10 Feed and -8 Return, but I'm also running an Aeromotive fuel pump controller to reduce flow at lower RPM's.