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> Fuel return with carbs- needed?
tornik550
post Nov 24 2018, 02:17 PM
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I recently purchased a PMO carb setup for my /6. My car has never used a fuel return hose since I purchased it many years ago. Do I really need to use the fuel return? My car is just for street driving. I am not really even sure what the fuel return is used for. I am trying to avoid using it because the fuel return lines in the tunnel have been removed by the previous owner and I really don’t want to install new ones.
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914Toy
post Nov 24 2018, 02:30 PM
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QUOTE(tornik550 @ Nov 24 2018, 12:17 PM) *

I recently purchased a PMO carb setup for my /6. My car has never used a fuel return hose since I purchased it many years ago. Do I really need to use the fuel return? My car is just for street driving. I am not really even sure what the fuel return is used for. I am trying to avoid using it because the fuel return lines in the tunnel have been removed by the previous owner and I really don’t want to install new ones.


I have no return line, and have a low pressure (15lb) fuel pump followed by pressure regulator (2.5lb), feeding fuel to the carbs. Carbs are mounted on the manifold with thick heat insulating gaskets to prevent fuel boiling when the engine is shut down hot.
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SirAndy
post Nov 24 2018, 02:46 PM
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QUOTE(tornik550 @ Nov 24 2018, 12:17 PM) *
I am not really even sure what the fuel return is used for.

The fuel return keeps the fuel circulating through the system, thus preventing it from getting too hot (or even boiling) while sitting in the float bowls.
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Retroracer
post Nov 24 2018, 03:20 PM
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I run a similar setup to 914Toy. /6 engine running Zeniths with no return line.

Facet fuel pump (9lbs-ish) followed by a non-bypass fuel regulator set to 4lbs. Make sure to install the insulating washers under the manifolds and you should be good to go.

- Tony
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sithot
post Nov 24 2018, 03:47 PM
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You can dead-head with a pump making correct pressure.
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mb911
post Nov 24 2018, 04:35 PM
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I am using the PMO return regulator for my test stand and I would recommend this over a deadbeat setup exactly for the reasons sirandy mentions.
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Mark Henry
post Nov 24 2018, 04:59 PM
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Needed? No
Better set up? Yes.
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Retroracer
post Nov 24 2018, 05:04 PM
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- Tony
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914Toy
post Nov 24 2018, 05:47 PM
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QUOTE(Mark Henry @ Nov 24 2018, 02:59 PM) *

Needed? No
Better set up? Yes.



Aaaaah!, more stuff to fail (IMG:style_emoticons/default/biggrin.gif)
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Mark Henry
post Nov 25 2018, 09:43 AM
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QUOTE(914Toy @ Nov 24 2018, 06:47 PM) *

QUOTE(Mark Henry @ Nov 24 2018, 02:59 PM) *

Needed? No
Better set up? Yes.



Aaaaah!, more stuff to fail (IMG:style_emoticons/default/biggrin.gif)


How's that? Were every stock FI 914s going up in flames?
Almost every big HP set-ups uses a return. Deadheading is now mostly something done only on low HP engines.
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brant
post Nov 25 2018, 10:21 AM
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I agree fully that a return system would the correct method.

The factory did it for a reason
It helps reduce vapor lock and makes a very small gain in hp
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bbrock
post Nov 25 2018, 10:36 AM
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I'm not seeing how there are more parts to fail on a loop system. Both systems use one pump and one pressure regulator. The loop requires a bit more fuel line and a couple more fittings I guess. What am I missing? (IMG:style_emoticons/default/confused24.gif)
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porschetub
post Nov 25 2018, 02:30 PM
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A constant running low pressure pump would benefit from a return,an interrupter type pump low pressure one has no need for a return.
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Chi-town
post Nov 25 2018, 05:05 PM
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A dead head regulator is hard on high pressure pumps.

There's a return line there why not use it?

http://www.carburetion.com/Products/Produc...?Part=31800.064
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sithot
post Nov 26 2018, 09:41 AM
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QUOTE(Chi-town @ Nov 25 2018, 06:05 PM) *

A dead head regulator is hard on high pressure pumps.

There's a return line there why not use it?



(IMG:style_emoticons/default/agree.gif) My 911 had a high pressure CIS pump and PMO regulator which I removed and installed the carburetor version, Bosch #05802544985, used on 911-T and the 914/6. There is no need for a regulator as the this Bosch pump is pre-set for optimal pressure and the return is already designed into the pump.
As for a carburetor regulator, if you can get the pressure in range I'd prefer and Aeromotive or similar with return feature. Summit Racing or Jegs has a good selection.
https://www.aeromotiveinc.com/product/low-p...eted-regulator/
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VaccaRabite
post Nov 27 2018, 08:52 AM
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When my car had carbs I never bothered with a return line. Made the plumbing easier.

Zach
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