Return line?

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Return line?

Postby Andreasu » Tue Aug 16, 2011 4:45 pm

My car has to "fuel" lines coming into the engine bay. One at the driver side (That one was hooked up to the carb) and one coming up from the pass. side. Is the pass. side one a return line?


Thanks!
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Re: Return line?

Postby monzajer » Tue Aug 16, 2011 11:27 pm

I think you are referring to a vapor canister line. See if you can dig up a schematic here. I think one of the members put up something like this not too long ago. The hose in question could be a return line to the tank.

Someone have a pic of the canister set-up for Andy? I believe there were two different set-ups. A 3 hose and a 5 hose, but I may be wrong.

cheers, jer :mrgreen:
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Re: Return line?

Postby Andreasu » Wed Aug 17, 2011 1:35 am

monzajer wrote:I think you are referring to a vapor canister line. See if you can dig up a schematic here. I think one of the members put up something like this not too long ago. The hose in question could be a return line to the tank.

Someone have a pic of the canister set-up for Andy? I believe there were two different set-ups. A 3 hose and a 5 hose, but I may be wrong.

cheers, jer :mrgreen:


Ah, I just thought it might have been a return line, since the fuel tank got 2 lines :lol:
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Re: Return line?

Postby spencerforhire » Wed Aug 17, 2011 6:07 am

It is designed as a canister vent line, but could be used as a return line(for fuel injection) if you switch to a vented gas cap.
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Re: Return line?

Postby cjbiagi » Wed Aug 17, 2011 6:44 am

I have been using that line as a return line for about 30 years. I use a fuel filter for a early 80's Chrysler K car which has a small orifice and a extra port on it. Helps keep the fuel in the engine compartment cooler.
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Re: Return line?

Postby Andreasu » Wed Aug 17, 2011 11:15 am

I'm planning to use a bypass regulator, just to reduse the stress on the fuel pump :)
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Re: Return line?

Postby cjbiagi » Wed Aug 17, 2011 11:23 am

Funny you should mention that, with all the talk about failed in tank pumps and I have never had a problem with that. (Hope I am not jinxing myself) I wonder if having that return line so the pump is not dead-headed has made the difference?
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Re: Return line?

Postby Andreasu » Thu Aug 18, 2011 1:33 am

Well, if you use a high-velocity pump with 100+ gph, and a regulator that reduses that to 7-8 psi, it puts stress on the pump (From what I've heard). A regulator with bypass will reduse the wear on the pump, I assume :th:
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Re: Return line?

Postby gm_fan » Thu Aug 18, 2011 10:09 pm

I am using the vent line for a return line on my Monza. I have a port injected pump [45-60 psi] in my tank , and a holley pressure regulator to keep the pressure down to 6-7 psi to the carb. SEEMS to work just fine so far..and the vent line relieves all that backed up pressure...gm_fan
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Re: Return line?

Postby Andreasu » Fri Aug 26, 2011 5:38 pm

Vent lines out of the tank?
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Re: Return line?

Postby spencerforhire » Mon Aug 29, 2011 6:19 am

Yes; it originally went from the tank up to the charcoal canister under the hood.
The "fleet"-
72 Vega HB Drag Car -383/'Glide/9"(9.35@146.19)(5.94@117.28 1/8th)
77 Vega Estate wagon- project(someday)will have TPI305/T-5, S-10 spindles/axles
76 Vega GT- 400/4spd/9" retired from active duty(rusty)
06 Silverado 2WD ex.cab daily
03 Silverado 2WD ex.cab (retired)
06 Haulin' 20ft enclosed car transporter
06 GMC Canyon Shop truck
07 Colorado project( 5.3 4L60e swap)
99 Saturn SL1- wife's car
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07 Saturn Ion Redline project
and 4 more Saturn "parts cars"
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Re: Return line?

Postby Ishiftem » Fri Sep 23, 2011 5:13 pm

Do not run a bypass system for a carburetor!!! Leave that for the efi people and guys running in the 8s. We had a bypass system on one of our cars. Holley 150 pump with -8 line for a supply, berry grant regulator and -8 return line. Tank well ventilated. The car would not respond to any jetting changes and just sounded like it was laboring. Didn't sound happy. After speaking with the folks at Weldon, we disconnected the bypass system and dead headed it with a Holley big port regulator. With no other changes, we knocked over 3 tenths off our ET and gained 4 mph. Now that it is getting fuel, we can play with the jetting and get even more out of it. It was amazing. Though the fuel pressure was stable the whole run with the bypass system, dead heading it got us huge gains. This is on a low 11 second car weighing 3900 pounds.
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Re: Return line?

Postby Rickracer » Fri Sep 23, 2011 7:35 pm

Ishiftem, your story goes contrary to dozens and dozens of them that go the other way. But the difference is that the pump you were using doesn't move enough volume to support a return system, if you had used an in-tank TBI pump, you would most likely have had no problems. Also, the return should have been -6, there's really no need for it to be the same size as the feed line. Just for example, no OEM system uses the same size for feed and return, virtually ALL of them are 3/8" feed and 5/16" return. 8)
And one major major plus to a return system, cooler fuel, and as a result, no vapor lock, which can be a huge benefit on a street driven vehicle, especially a daily driver. 8)
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Re: Return line?

Postby cjbiagi » Fri Sep 23, 2011 8:20 pm

With the simple system I have the return is regulated by a very small orifice built into the fuel filter. I don't know the size but as I mentioned this is a filter for a early 80's Chrysler "K" car which was carburated. I'm guessing the orifice is maybe .030 - .040 or something like that.........you get the idea. This is combined with the stock V8 in tank pump. As mentioned I have been running this for over 30 years and I originally did it to cure a vapor lock symptom on very hot days. I use the original vapor line as my return.
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Re: Return line?

Postby Ishiftem » Fri Sep 23, 2011 8:37 pm

First on the return line. Never run a return line smaller than the feed on a bypass system. The oem that you refer to is efi. I'm talking carbs. The smaller return causes a restriction that will not allow you to turn down the pressure making the regulator useless. We had a -6 return originally. Could not turn the pressure down past 7 pounds. We run two afb carbs and 6 is the max. Secondly having a smaller return line keeps pressure in that line until it dumps in the tank. It is that point that the fuel will "boil" or vaporize due to the pressure change. This aerates the fuel in the tank and causes it to oxidize. Running an line equal to or larger on the return after the regulator gives the those vapors a chance to reconstitute with the liquid fuel before reaching the tank. The problem with a bypass system is pressure. The pump we have for example puts out 17 pounds. The entire line from the pump to the carbs however only will only see as much pressure as the regulator is set to. In a carb application that is usually 6-8 pounds. When you leave the line, the fuel will literally stall. Case in point. A guy we know has a low 9 second car. His pump pressure was 24 pounds to the regulator. After turning the pressure up to 27, he knocked a half a tenth of his 60 ft time. Most if not all modern systems that have a bypass do this right at the pump exit that then goes to the tank. This ensures adequate pressure to the regulator. Having a bypass regulator after the carbs only leads to problems. This info is not contrary to anybody and is readily available.
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