How do I hook up a fuel return line to a Weber DGV?

[Will]

I'm trying to hook up a Weber DGV to my Datsun 710 with an L20B. The carb I'll be using has a manual choke, and the DGV that was on the car when I bought it has an electric choke. I can't seem to figure out where to hook up the fuel return line.

 

There are two fuel lines coming in to the engine compartment next to each other, one is 1/4" and the other is 3/16". I can't remember how the return line (the 3/16" line) was hooked up before - there doesn't seem to be anywhere for it to hook up.

 

Below are some images of the two carbs, and where I think everything goes. The carbs don't have a pipe where I think the return line fitting should be - can a bit of appropriately-sized pipe be pressed into place? Or is this not used on some DGVs?

 

[ggzilla]

There is no fuel return on that carburetor. That's an untapped boss.

[Will]

There is no fuel return on that carburetor. That's an untapped boss.

I see. thanks - any ideas on how I should route the unused fuel return line?

[ggzilla]

Just the same as with the stock carb. The return is before the carb.

 

Weber does not need a return line.

[datzenmike]

Will your L20B should have a metal line from the stock pump to the Hitachi where it turns around and comes back to the pump. At that end there is a restriction with a small hole in it. A hose connects it to the return line to the tank. Without the restriction fuel would just take the easy way back to the tank and there would be no fuel pressure. You should be able to use this with a weber.

[Will]

Will your L20B should have a metal line from the stock pump to the Hitachi where it turns around and comes back to the pump. At that end there is a restriction with a small hole in it. A hose connects it to the return line to the tank. Without the restriction fuel would just take the easy way back to the tank and there would be no fuel pressure. You should be able to use this with a weber.

 

Thanks! Now I gotta track down that metal line - I'm sure its around here somewhere.

[datsunaholic]

Just the same as with the stock carb. The return is before the carb.

 

Weber does not need a return line.

 

Webers don't need one until they do.  With the larger L20B pump, they almost always do, they have enough volume to over-pressre the float, and then flood.  The small L16/L18 pumps don't seem to do that.  Some folks run a regulator, which I've never had work.  Either they leak or they don't have a happy medium.  Either they Starve at freeway speeds/accelerating or flood going down hills/idle.  The stock return line, never had the problem as long as its not clogged.

 

The stock return line looks like this:

 

 

The unit also contains the carb vacuum hard lines.  Folks get rid of them to "clean up the engine" then make things worse adding pressure regulators and miles of rubber hose.

[ggzilla]

It's the pressure that overwhelms the weber carb. The 32/36 requires a low-pressure fuel feed (2.5 to 3 lbs). The L18 fuel pump puts out 3.0 to 3.8 psi. So either use a return with bleed (larger than the stock bleed), a fuel pressure regulator, or set the float lower than normal to maintain the correct fuel level (which often works depending on the needle and seat).

[Will]

Thanks everyone! This is exactly the information I was looking for. Looks like the metal fuel line vanished before I bought the engine, but luckily I have a spare (from the old L18, I think)

[Will]

I just noticed some more details in this photo:

 

 

My metal line is a bit more simple - no attached vacuum lines.