Fuel pump setup for dual 40 DCNF?

AngleT

AngleT

Always more tuning to do
I have a couple question for you X heads who are running dual 40 DCNF carbs.
1. What type and size of fuel pump are you running?
2. Are you using a fuel pressure regulator?
3. At what pressure is your system running?

Would this be too much fuel pump for my setup?
http://www.jegs.com/i/JEGS/555/15914/10002/-1

(105 GPH "free flow" turns into about 70 GPH at 5 PSI)

I found a website that had a math calculation for the Gallon Per Hour (GPH) needed for my setup and the math came to 16GPH. That seemed low considering the solid state (rattle can) fuel pumps run about 30 GPH. I have been told by a lot of people that the solid state fuel pump wouldn't pump enough volume for my engine and that I should have a pressure regulator for any setup. Just wanted to take a survey to see what the general consciences was.

Thanks,
 
Sounds like things are progressing well. I use this
http://store.summitracing.com/partd...LY-12-801-1&N=700+4294836965+115&autoview=sku

Plus this

http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY-12-804&N=700+115&autoview=sku

Plus a fuel pressure gage that screws into the regulator.

I don't necessarily recommend the Holly pump. I have had issues with it failing and know of other folks with that same issue. I had one replaced under warranty after much deliberation. The short story is if you use the Holly pump you better have another on the shelf ready to go. You can see the specs for reference though. Another key point is to make sure you use a good fuel filter. I know of several people having flow issues that used the glass see-though filter. I have used the plastic see-through filters with great success (fram) - others don't like them apparently but I am not sure why.

For location it is best to put the pump near the bottom of the car. It is easier on the pump if the fuel maintains a pressure "head" , same concept as siphoning. Many people have mounted the pump on the carb fan studs at the top of the engine, it works, is tidy, and easy to do, but the pump has to work harder to pull the fuel up to the top of the engine, especially at start up; I would expect premature failure.
 
fuel pressure

What pressure should I be running. The one I posted comes with a 4.5-9 lbs and yours is a 1-4 lbs. Is 4.5 lbs too much?
 
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4.5 psi is too much for a set of DCNFs.. They work properly at 2-3 psi. Install a regulator or use a fuel pump with internal regulation. The rotary pumps are perfered over the pulsers (OK with a pressure reservoir to even out the pulses) as the constant pressure won't cause intermittent float flooding.
 
Book says

it should be between 2.1 - 2.8 psi of fuel pressure. So, I guess its a low pressure/high volume setup I'm looking for.
 
psi

well i am running 4.5 psi on my track car and it runs great. i have been told that they should run between 4psi & 5psi. i am running a holly blue electric fuel pump and regulator. can post pics if you would like.
 
stock pump

With dual DCNF's I've run with a totally stock mechanical Fiat pump.

JimV
Cincinnati
 
Return line.

You need to keep the fuel moving as heat soak will be a problem with the DCNF's. With the regulator the over pressure returns to the tank and keeps the fuel moving and cool. Also the electic can be started before the engine is cranked to purge out the hot fuel in the lines, then a start can be done.

TonyK

Grimsby Ontario Canada.
 
Holley blue here as well

on my spider that is. They're noisy, but been 100% reliable for me for 10+ years. I imagine a stock mechanical pump would work fine too. Make sure you have a return line, like Tony said, it's best to keep the surplus fuel flowing.

How are you going to feed electricity to the pump? Mine runs off a oil pressure relay, and so it doesn't pump until oil pressure has built up. This actually works well when the car has sat for some time; it primes the engine with oil before it starts up.
 
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