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Discussion Starter #1
Hi,

When converting a Twin Spark engine to run on twin Webers, what's the best way to deliver fuel to the carbs?

I have the glass bowl fuel filter/regulator for a twin carb Nord, but I'm wondering what type/specification of electric fuel pump I should use in the engine bay given that the Twin Spark engine does not have a provision for a mechanical Nord-style fuel pump.

Should I also consider installing a low volume fuel pump back near the fuel tank to further assist constant fuel flow through the system?

Any advice would be most appreciated.

Regards,


Nick
 

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i would recommend a holly red fuel pump, pumps a good pressure and lots of fuel,
however any pump capable of 5-7 psi should do the trick, a surge tank shouldnt really be needed ( i could be wrong ) because unlike efi pumps these pumps are designed to suck as well as push fuel. and are normally used for lift pumps in an efi set up.
cheers, Brad
 

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5 to 7 lbs will lift the floats and needle. Way to much pressure for Weber applications. The correct modern pump is a low pressure, high volume pump like the Facet that gives 2.75 to 4 psi and 36 GPH volume. These are normally mounted in back, near the fuel tank. Your pressure regulator needs to be adjusted for 3 psi. A major role of the regulator is to damp out the fuel pulses with a diaphragm to avoid hammering divots the the Weber float adjustment paddle. This pump is available in the U.S. from Centerline or International Auto Parts, and probably sources in Australia as well. Do not bother with any of the fuel injection pumps.
 

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Discussion Starter #4 (Edited)
Hi Brad & Gordon,

Thanks for the replies.

Based on your tips, I did some additional "googling" and found that Weber Performance here in Melbourne Carter Electric Fuel Pump P4070 - Ideal for use with Weber Carburettors Weber Performance Carburettors recommends a Carter P4070 Electric Fuel Pump for use with Weber carburettors. Apparently it provides 72GPH at 4-6 PSI, and can be used with or without a regulator.

I'm thinking about mounting a Carter pump back near the fuel tank (apparently electric pumps prefer to "push" rather than "pull" fuel??), and then I would still use the stock Nord regulator in the engine bay, as it also incorporates a fuel filter. What do you think?

Regards,


Nick
 

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perfect, i know that efi pumps dont like to suck, but as i said i think low pressure pumps can, as they are normally used to such the fuel from the tank and supply it to the surge tank. so my guess there no worries,

intersting you say 7psi is too much? we set my cousins datsun running twin 40 dcoe's to a max of 6-7 psi, runs like a dream...
 

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Discussion Starter #6
Hi Brad,

Taking a "belt and braces" approach, I think perhaps mounting the low pressure/high volume Carter pump close to the fuel tank (ie so it doesn't have to suck fuel down the whole length of the fuel line) might be the best approach. Thanks for your help.

Hi Gordan,

Further to Brad's question on the appropriate fuel pressure, and your suggestion above, do you happen to know if the stock Nord fuel regulator is adjustable (ie so that it could be set at the 3 psi level you suggest)? Thanks also for your help.

Regards,


Nick
 

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Fortunately, Nick, that's where I learned about the 3 psi. 40 + years ago we ran dual pumps on the GTA's and they had this pressure regulator / filter assembly, the FISPA FRB 11. The only way we could get more pressure was with that out of the circuit. Webers dribbled, and flooded, floats got dings in the adjustment paddle, causing the needle ball end to sometimes jam the assembly. Research showed the FRB 11 was there for a reason, and GENERALLY, with the adjustment screw set so that about 3 threads showed above the threaded hole, would give ABOUT 3 psi. The unit also damped the pulses from the pumps, float hammering was greatly reduced. My current GTA engine runs only the single FACET pump, with the FRB 11 regulator / filter. Plenty of volume. I hope this helps.
 

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Discussion Starter #8
Hi Gordan,

That is excellent information, thanks. I take it that the "FISPA FRB 11" is what I have been referring to as the "stock Nord fuel regulator"?

Thanks also for the advice on adjusting the fuel pressure to 3 psi.

I understand that the Carter pump is a rotary design and therefore is less prone to pulsing and hammering, but as I said in response to Brad, I favour a belt and braces approach, so retaining the stock fuel regulator/filter seems like a sensible approach.

Regards,


Nick
 

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Based on your tips, I did some additional "googling" and found that Weber Performance here in Melbourne Carter Electric Fuel Pump P4070 - Ideal for use with Weber Carburettors Weber Performance Carburettors recommends a Carter P4070 Electric Fuel Pump for use with Weber carburettors. Apparently it provides 72GPH at 4-6 PSI, and can be used with or without a regulator.
I have a Carter P4070 on my Spider. It is a good pump. It is noisy and it needs a regulator. Mine is set to 3 psi.
 

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I have a Carter P4070 on my Spider. It is a good pump. It is noisy and it needs a regulator. Mine is set to 3 psi.
I have the Carter on one car, and the Facet "Bendix" style pump on another. Part FP455 at Centerline. I prefer the Facet, both because it has a built-in filter and because it's much, much quieter.

-Jason
 

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hi nick, just so wear clear i did mean mount the pump near the fuel tank,
cheers, Brad
 

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Discussion Starter #12
hi nick, just so wear clear i did mean mount the pump near the fuel tank,
cheers, Brad
Hi Brad,

Yep... that's what I understood you meant as well.

Cheers,


Nick
 

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Mount it near the tank if you want but there is no need to . I had the exact same pump for years when I had Webers and it worked great mounted in the engine bay where the fuel filter/ regulator had been (under the carbs on the fender) . The advice about fuel pressure is right on .
 

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pump location is NOT critical..however.."some" pumps will run cooler and last longer by the tank...but know this when a "cheep" pump fails it may very well catch fire.(ive had 3 go bad 2 went in a ball of fire 1 in a cloud of smoke 2 of them were carters 1 was a holley)..at 3psi it wont make a huge mess if its in the engine bay..thus why i prefer to have the pumps in the bay generaly as high up as possible with nothing neer them to burn
 

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Discussion Starter #16
pump location is NOT critical..however.."some" pumps will run cooler and last longer by the tank...but know this when a "cheep" pump fails it may very well catch fire.(ive had 3 go bad 2 went in a ball of fire 1 in a cloud of smoke 2 of them were carters 1 was a holley)..at 3psi it wont make a huge mess if its in the engine bay..thus why i prefer to have the pumps in the bay generaly as high up as possible with nothing neer them to burn
Mmmm.... the engine bay does sound like the slightly lesser of two evils. I'd prefer not to have a flame throwing fuel pump too close to the fuel tank :D
 

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I've used rear mounted pumps on Ferrari's and my Alfa's for literally hundreds of thousands of miles, including racing, since 1962. I've had hose leaks from line deterioration, and a vane type aircraft pump fail with my Ausca spider. Had a Bosh type just quit, but nothing ever even became warm. My pumps have always been run through my fuse blocks.
It seems if these pumps, properly fused, caused "a ball of fire", they would be a very bad bet for the intended use, no matter WHERE they are mounted! Just my opinion.
 

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agreed and thus why i prefer bosche pumps even if its an efi pump regulated down.....there built to take a long hard life...unlike most modern disposible crap
 

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Very likely. The design is similar. This is just my opinion however.
 
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