electric fuel pump return line size?

[Josh]

In the BarryGrant schematic I have for my 220HR pump, it requires a -10 return line, but only a -8 feed line from the pump to the carb? Why the -10? There should be less fuel returning to the tank then was sent to the carb... I was thinking I would just use the stock 3/8" feed line as the return line and be all set, but I guess not. Is there any leeway in this set up? This is in a street car with a 540 BBC and a 950 DP carb.
Thanks!

[Josh]

Any ideas on this? I am needing to order my parts ASAP, Thanks!

[jocko124]

I'm pulling this info. off the RobbMC Performance website:


When used with a sufficiently large return line, bypass regulators produce less pressure drop at full throttle.

When using the regulator in the bypass mode, a return fuel line is required from the bottom of the regulator back to the fuel tank/cell. For proper regulator function, there must be very little resistance to flow in the return line. Avoid 90 degree fittings. Connect the return line near the top of the fuel tank/cell. Use the following as a guideline to determine the minimum return line size:

Fuel pumps up to 70 gph: 5/16” or -4AN
Fuel pumps up to 100 gph: 3/8” or -6AN
Fuel pumps up to 180 gph: ½” or -8AN
Fuel pumps up to 300 gph: 5/8” or -10 AN


This info is for an electric fuel pump being used with a regulator in Bypass mode.

[Zee]

Return line should be the same as the pump line. Some say larger as it does not see the as much pressure but often has the same routing (restrictions). IMO, -10 is overkill unless you have a lot of 90 degree fittings and such. At the end of the day, it all has to go through two tiny needle and seats.

[doghouse]

for there A1000 FI pump, (capable of 1000HP turbo'd)
-10 feed and -6 return,
I use a -10 feed and combo of -8 and 2x -6 return lines.
817hp to rear wheels, from a six cyl.

[DButler]

I installed a BG400 on my twin turbo setup and I am feeding it with -10 and returning it with -8. I would recommend going with a bigger return line because until I jumped up to the -8 my fuel was bottle necking at the regulator. They recommend the pumps to be at 18 to 20 psi at the pump and regulate it down to about 7 or 8 psi at the carb. So you are actually returning a good amount of fuel.

[Skip Fix]

They recommend the pumps to be at 18 to 20 psi at the pump and regulate it down to about 7 or 8 psi at the carb.

I think that is the reason for the larger return line.