upgrading to 4bbl carb on my series III, there seems to be 2 fuel lines what to i do?

[gobie desert]

hey all, i am switching to a 4bbl on my series III v-8, the old zeniths fuel line seem to have 2 lines going into it. one comes from the filter the other i guess comes from the tank. anyone do this conversion? if so what do you do with the lines. are they both fuel lines? do they both get hooked back up? thanks.

[BackInA88]

Is one maybe a fuel return line???

[64 Wagon]

Or do you have two gas tanks?

[gobie desert]

i was thinking one was a return line as well. i followed the line and it seems to run back to the gas tank. there were at some point 2 tanks but the aux tank seems to have been long out of commission. the tanks top was cut open so i guess it became a storage and there are no lines that go to it. is the return line more for the carbs and is it needed when doing the conversion?

[BackInA88]

I seem to remember reading somewhere that some Webers used a fuel return line.
Has for needing it for your conversion I guess that would depend on your new carb, and fuel pressure coming out of your fuel pump.
I think most US type 4 barrels like 6 to 8 psi IIRC?


Steve

[gobie desert]

i am converting to the holley 390cfm, edlebrock intake. i have ran holleys on other application without ever running a return line. from street economy to full on wild race. so do i get rid of the return line? if so do i just block it off at the tank?

[siiirhd88]

Yes, just block off the return line at the tank. As you said, the Holley won't need the return line. I run the generic vacuum secondary 600 cfm Holley 4V on the 3.9 V8s in my '75 88 and the wife's '68 109. I couldn't see spending the extra $ for the 390 cfm carb.

Bob

[gobie desert]

thanks. hey how do those 600's run on that engine? i was considering doing that cause i have a 600 that needs to be rebuilt but felt i would be over carbed. i got my 390 for 200 bucks, not bad considering they are quite popular.

[siiirhd88]

The 600 CFM Holley runs great. No complaints at all. The wife's 109 with 3.9 V8, R380 5 speed and RR 3.54 axles is getting 20 mpg on the highway. No problem with power, and the rear barrels never need to open.... You could probably get by with a Holley 2V and adapter on the 4V manifold.

Bob