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Re: How too add a fuel return line to fight vapor lock ?
[Re: Mr.Yuck]
#811205
12/13/10 01:19 PM
12/13/10 01:19 PM
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Joined: Oct 2010
Posts: 606
Montana
Yancy Derringer
mopar
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mopar
Joined: Oct 2010
Posts: 606
Montana
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Quote:
You should'nt need a return line on a even a semi-wild build.
I'm not sure I agree with a general statement like this. It has been MANY years now since even the factories put vapor return on cars
First time I ever saw one was on my '70 Roadrunner, 440 sixpack.
With today's poor gas and poor high temp properties, I think vapor return is a great idea. Any car new enough to have had factory carbon canisters can implement it easily
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Re: How too add a fuel return line to fight vapor lock ?
[Re: convx4]
#811207
07/03/14 02:51 PM
07/03/14 02:51 PM
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Joined: Jan 2003
Posts: 27,303
Rio Linda, CA
John_Kunkel
The Erection Connection
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The Erection Connection
Joined: Jan 2003
Posts: 27,303
Rio Linda, CA
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To prevent vapor lock there's no need to return the fuel all the way to the tank, a bypass hose with a small restrictor between the inlet and outlet of the pump will do it...sixties CHP 440 cars had such a setup.
The INTERNET, the MISinformation superhighway
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Re: How too add a fuel return line to fight vapor lock ?
[Re: John_Kunkel]
#811208
07/03/14 03:28 PM
07/03/14 03:28 PM
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Joined: Oct 2006
Posts: 7,395
Iowa
burdar
Owen's Dad
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Owen's Dad
Joined: Oct 2006
Posts: 7,395
Iowa
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Quote:
To prevent vapor lock there's no need to return the fuel all the way to the tank, a bypass hose with a small restrictor between the inlet and outlet of the pump will do it...sixties CHP 440 cars had such a setup.
Picture?
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Re: How too add a fuel return line to fight vapor lock ?
[Re: Kcracegirl]
#811209
07/03/14 03:29 PM
07/03/14 03:29 PM
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Joined: Apr 2012
Posts: 18,880
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RSNOMO
Moparts Torchbearer
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Moparts Torchbearer
Joined: Apr 2012
Posts: 18,880
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Quote:
We have a 72 Roadrunner with the same vapor lock issues. If it is 60 degrees out the car runs pretty good. If it is 95 out we can go about 13 miles and it starts acting like it is fuel deprived. . Our old charcoal canister system was shot so we had to remove it. We added a spacer, wrapped the metal fuel line that runs to the carb. We want to add a return line but Our sending unit doesnt have a return line nipple but we have 4 venting nipples off the rear/top of the tank. Can we run a return line to one of those? If so, does it matter which one? We have a mechanical fuel pump so should we make a heat shield for it or switch to an electric fuel pump? Thanks for the help- it's frustrating to say the least not being able to take our car out and enjoy it. Teri
Another option would be to just use the OEM system if the car still has the components...
Get a '72 Service Manual...
I've got OEM 'fuel system' components on a '71 B-body...
Been in 95 degree plus heat more than once...
No vapor lock issues...
The system works if set-up properly...
(And no, you do not need to go to an electric fuel pump)...
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Re: How too add a fuel return line to fight vapor lock ?
[Re: burdar]
#811210
07/03/14 04:09 PM
07/03/14 04:09 PM
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Joined: May 2005
Posts: 5,021
Florida
BDW
master
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master
Joined: May 2005
Posts: 5,021
Florida
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Quote:
Quote:
To prevent vapor lock there's no need to return the fuel all the way to the tank, a bypass hose with a small restrictor between the inlet and outlet of the pump will do it...sixties CHP 440 cars had such a setup.
Picture?
I'd like info on this too, my 70 Challenger has issues in the summer.
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Re: How too add a fuel return line to fight vapor lock ?
[Re: mkdart]
#811211
07/03/14 04:14 PM
07/03/14 04:14 PM
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Joined: May 2005
Posts: 5,021
Florida
BDW
master
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master
Joined: May 2005
Posts: 5,021
Florida
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Quote:
My vapor lock mods are,3 nipple fuel filter,1/4 inch line back to the filler neck and a plastic carb spacer. Mike
Can you post a pic / PN for the fuel filter, what applicant.
Where do you mount, any other mod' or just run the 3rd line back to the fuel tanks?
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Re: How too add a fuel return line to fight vapor lock ?
[Re: John_Kunkel]
#811213
07/03/14 07:29 PM
07/03/14 07:29 PM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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Quote:
Quote:
Quote:
To prevent vapor lock there's no need to return the fuel all the way to the tank, a bypass hose with a small restrictor between the inlet and outlet of the pump will do it...sixties CHP 440 cars had such a setup.
Picture?
No pic. On the inlet side of the pump there was a small brass "T" fitting, ditto on the outlet...a 1/4" hose connected the two, inside the hose was a brass "pill" with a small hole drilled in it.
This allowed some of the pressure from the outlet side to recirculate to the suction side but the volume was so small that it didn't affect performance.
Not sure if this was a factory "cop car" item or if it was added by the CHP.
Yes this can done, but it's not optimal because it does add turbulence at the inlet of the pump and could even return some vapor at the inlet of the fuel pump which is very bad. Yes mechanical fuel pumps can tolerate this much more so than a positive displacement electric fuel pump could.
I got a feeling it was a trick/attempt at curing vapor lock they used on cars that operated in extreme hot conditions.
FWIW I have a stock hemi fuel system on my hot little 340. I mean stock hemi with the vapor separator that mounts to the fuel pump and return line. Stock stuff and have driven the car in hi altitudes and high temperatures(115 degrees) for extended periods of time with never any trouble. Year after year, Stock works.
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Re: How too add a fuel return line to fight vapor lock ?
[Re: Kern Dog]
#811215
07/03/14 10:42 PM
07/03/14 10:42 PM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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Quote:
I too have considered using a few tactics to end vapor lock.
A carb spacer is out. The air cleaner lid is already too close to my hood as is and I refuse to add a scoop to a 70 Charger hood.
I have a repro 1/4" vent line that is in the car but I've never hooked it up. I read where guys have used a 3 nipple type filter but it has me curious: How could fuel pressure to the carb be adequate with two points of exit in the 3 nipple filter? Wouldnt the gas just follow the unrestricted path back to the tank and never build pressure at the carburetor?
Yes it would, you need to provide a .050" restriction in the return line.
The original factory ones had like a .057" restriction in the return nipple and the repo have something closer to .100", which is too big.
I used a holley jet as my restrictor.
I believe the factory style vapor separator is better for the job than a aftermarkt with third nipple. I think it does a better job of sending vapor back to the tank. 
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Re: How too add a fuel return line to fight vapor lock ?
[Re: Challenger 1]
#811216
07/03/14 10:46 PM
07/03/14 10:46 PM
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Joined: Apr 2012
Posts: 18,880
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RSNOMO
Moparts Torchbearer
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Moparts Torchbearer
Joined: Apr 2012
Posts: 18,880
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Quote:
I believe the factory style vapor separator is better for the job than a aftermarkt with third nipple. I think it does a better job of sending vapor back to the tank.
Been using a 3-nip 'fuel filter' for beaucoup years with no issues...
A fidee-dollar can with a screen ain't of no value to me...
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