Fuel return line routing

[Habitat.pat]

I’m adding a fuel return line to my 67.5. I have a 70 fuel tank with the canister port capped & electric fuel pump on frame by tank. I bought the return line from Classic Tube but can’t figure out the routing.

Does anyone have photos of the return line underneath? Is it routed on the outside of the right frame rail like the fuel supply line or is it on the inside of the frame rail? It appears that my line is not bent correctly but I can rebend it as needed.

Thanks for your help.

Peace, Pat

[jrusso07]

According to this diagram it runs next to the fuel supply line

https://www.carpartsmanual.com/datsun/s ... tank/evapo

[Habitat.pat]

Thanks. I’m hoping for actual photos or description because that drawing is not close to the path of the lines, just showing what connects to what.

Peace, Pat

[jrusso07]

I will try to get a picture(s) with the cars on the ground.

[Habitat.pat]

Thanks!

[Stick]

Not sure on the 67.5 but the 69 (with SU's) runs from the back of the rear carb into a hard line. The hard line runs across the firewall to the passenger side and dips down under the passenger side and runs along the outside rail (next to the supply line). There is a connector just below the passenger side door and it runs all the way back to where the axle is and transitions from hard line to flex going and and over the axle and runs to the back of the tank. Mine follows the supply line on the same side of the frame the entire way.

The larger of the two lines is the return line.

[Habitat.pat]

Thanks, I’ll see if the Classic Tube lines fit that way. I expect that I’ll have to touch up some of the bends but want to be sure before I do.

Peace, Pat

[redroadster]

I've known guys that installed a T in the return then 2 motorcycle tank shut off valves, so they can pump fuel out to a tank with it running
Did you know the return line system heats/ warms the gas ,colder fuel doesn't aireate as much as 70 ° gas
And is a safety improvement in cold weather , Iowa - MN, and such

[Habitat.pat]

Sounds interesting!

[Pjackb]

Have you done this yet?

[Habitat.pat]

Still working on it. Hopefully I’ll get back to it this coming week or next.

I figured out how they intended them to fit & now need to install the regulator up front, insulate the line & secure it. I decided to use 3/8” fuel line over the 5/16” stainless steel return line. For both insulation & rock shielding.

I hope to get this completed before my trans comes back from being rebuilt. Having the engine out makes it much easier to route the line.

Peace, Pat

[Pjackb]

When you do if you don’t mind please post some pictures
I’m putting in an “improved” engine in my 67.5 next spring and going full EFI which requires me to run a return line so looking for examples of how folks have routed the lines
Thanks

[Gregs672000]

When you do if you don’t mind please post some pictures
I’m putting in an “improved” engine in my 67.5 next spring and going full EFI which requires me to run a return line so looking for examples of how folks have routed the lines
Thanks

As an FYI, I routed my return line back to my 1 gallon swirl tank that houses the fuel pump and that then overflows to the main tank through a separate tube as needed. Even with an inline cooler, mounted under the passenger seat area under the car, I'm finding high fuel temps. I've used the stock tank vent tube that ties into the fuel neck inside the trunk and installed a T fitting in that line for the swirl tank overflow. I was able to access this line through the access plate in the trunk. I may decide to route the return directly to this line so hot fuel is returned to the main tank to help cool it off. I'm a little concerned about making sure the line and fittings can handle the pressure and flow volume, but as I understand it there is very low pressure on the return, though I have never tested pressure or volume on that line. If this does not work then I'm considering adding another return fitting to the main tank and routing to that. When I was designing the system I spent some time searching for fittings that can be secured/sealed without having access to the inside of the tank. As I recall they do exist but will have to search again. I'd rather not remove the tank as I know bolts will likely snap etc. It may be possible to gain some limited access for tools via the sending unit hole. If you already have the tank out to fit a fuel pump then you can probably add a fitting fairly easily. I think I'd put it on a side panel vs on top due to clearance. I do worry some about sparks from the drill and fuel fumes...please be careful.

Happy to share anything I've learned about EFI and tuning.

[Gregs672000]

In addition, think some about how you're routing your fuel lines to feed the injectors. I ran mine close to the engine which tends to expose them to exhaust and engine temps, similar to stock lines. I was very surprised to find how hot my swirl tank was getting, particularly with higher summer heat... hot to the touch. I think this temperature has influenced my tuning parameters and overall running. I've been researching insulating wraps to help reduce this... some are more effective than others with different pricing that reflects this. At some point I'll update my thread on converting to EFI.