Dual Tank Plumbing Advice and Considerations

Hi all,

Looking for advice, suggestions, schematics on how to plumb a 2 tank setup for an RCR40. I am planning to run the tanks independently with no crossover and feeding a quartet of Webers which are plumbed in series. There is no provision for fuel return, so will be plugging those holes in the tank.

I am using 2 separate fuel pumps, each controlled by an individual switch with the idea that the two lines would come together in a T then on to the carb setup.

Here are some questions:

1. The Facet fuel pumps have a built in filter screen. Should I use an additional filter? If so, what size and where? Should this be between the tank and the pump, or downstream of the pumps where the two tank lines T together?
2. What one-way check valves should I use to prevent one tank from pumping fuel into the other? Where should these be located?
3. I'd like to use Aero-quip style braided lines with the red/blue AN fittings. What gauge should all this plumbing be?

Anything else I haven't thought of or a diagram of someone's similar system is much appreciated!
 

Ian Anderson

Lifetime Supporter
Supporter
I would suggest
tank to filter to pump to non return to Y piece to filter and pressure regulator to carbs.

I would also suggest that the Facit will not move enough fuel.

Make sure your fuel line is Ethanol proof. Especially if braided as it covers the deterioration of the line.

Ian
 

Terry Oxandale

Skinny Man
Depending on the each tank's design, have you considered a small sump tank in case the tanks get low? Lastly, I personally use a prefilter for any device that has a built-in filter. A cheap, press-on, similar to the Fram G3. Amazing the garbage it has stopped before getting to the pumps.
 
Facet pumps are no go. Not enough flow.
Better use 2 Holley red pumps both into check valve both into 2 filterking regulators/filters into a T to the carbs.

From the carbs you can run a T with a .5mm restrictor as a return to both tanks. It will prevent boilover from the carbs and also depressurerise fuel lines when fuelpumps are shut off.
 
Thank you, all for the super quick and helpful replies!

With respect to the Facet -- it is what RCR sent me with the car. Box says it puts out 12-15psi at 60" lift and I know the Webers need only 2.5 -3 psi. Why would they be inadequate? This motor is a 363 with Weber 48IDA's making 467HP.

Also, is AN-6 appropriate gauge for the fuel lines I need to make or should I use AN-8?

IMG_7923.jpg
 

Ian Anderson

Lifetime Supporter
Supporter
Google brought up Pegasus.
They say 20gph at 8 psi. * 3.785 = 75700 CC per hour /60 = 1261 CC per minute

your engine 476 hp at 15cc per hp per minute = requirement for 7140 cc per minute

I would suggest your pumps will not flow nearly enough!

ian
 
I'll be happy if I get to the point where I actually have a fuel system where I can even turn on a pump! This project has been daunting beyond what I could have ever imagined and I certainly would not have been this far along if not for the great folks like you on the forum helping me out. A lifesaver and much appreciated!
 
Facet silver Top, 36 GPH free flow, 23 GPH @ 2 psi. 11.5 GPH @ 4 psi.
Facet Red Top 40 GPH free flow, 35 GPH @ 2 psi. 20 GPH @ 4 psi
Facet Blue Top, 45 GPH, 38 GPH @ 2 psi. 23 GPH @ 4 psi

Facet Dura Lift 40285, 33 GPH Free Flow, 4-7 psi @ no flow.
Facet Dura Lift 40222, 33 GPH Free Flow, 9-11 psi @ no flow, 17 GPH @ 4 psi
Facet Dura Lift 40290, 50 GPH Free Flow, 12-15 psi @ no flow, 20 GPH @ 8 psi
Holley Red flows 97 Us Gph free flow - 67 Us Gph @ 5psi
Carter P4600HP flows 100 Us Gph free flow.

Steward Warner 240A, ?

Webers run 4 psi fuel pressure.
Holleys run 7 psi fuel pressure.

The more pressure a pump has to deliver the less GPH is pumped by the pump. That’s why we are not interested in free flow numbers given by the manufacturers.

Modern fuel pump calculators calculate:

250 bhp you´ll need 24 GPH @ 4 - 7 psi, that’s about max a Facet Dura Lift (40290) can handle.
350 bhp you’ll need 33 GPH @ 4 - 7 psi, so that leaves a Facet Red & Blue Top out.
400 bhp you’ll need 37 GPH @ 4 – 7 psi.
4 psi for the weber carb, 7 psi for a Holley carb.

Facet Red & Blue top pumps have no flow at 7 psi while Holley recommends 7 psi at idle, and a minimum 4 psi at engine redline for their carbs.

You also don’t want to be on the edge of a pumps capacity cause as the pump wears it affects its GPH.
Especially the Facet Red & Blue wears out fast. Unless you don’t drive that often.

If you run multiple carbs, you’ll have to take into account multiple float chambers have to be filled at the same time and rate. And as multiple carbs have multiple pump jets you’ll need some extra capacity to keep up the demand.
 
Thanks, JP, for the detailed analysis. Since I'm looking for 4 psi (Webers), and you say my Facet Dura Lift can put out 20GPH @ 8psi, does that mean it puts out 40GPH @ 4psi? And, if so, is that adequate to support 470hp through 4 Webers?
 
JP

NOW YOU HAVE ME THINKING ABOUT MY GPH. I AM NOT AT WOT VERY OFTEN . WOULD THE POWER FALL OFF AS THE MOTOR GOES INTO A LEAN SITUATION ? RUNNING FACET RED TOPS
 
JP

NOW YOU HAVE ME THINKING ABOUT MY GPH. I AM NOT AT WOT VERY OFTEN . WOULD THE POWER FALL OFF AS THE MOTOR GOES INTO A LEAN SITUATION ? RUNNING FACET RED TOPS
Yes, had that situation multiple times with red tops running more than an hour on roadtrips. Holley Red pumps cured that (I am running AFR gauges in almost everything I build & drive).

When Facet pumps get warm or hot, they loose volume and pressure.
Holley Red is a differend type pump, no plunger but vanes.

I have seen cars racing at Spa Classic, Summer Classic and Sixhours loosing the game by Facet pumps.
Unless you have an AFR gauge you'll never know whats happening.
 

Neil

Supporter
Walt- Figure your fuel consumption at 0.5 lbs per horsepower- hour. Multiply your horsepower (470 BHP) by time (1 hour) and multiply by 0.5. This gives you the amount of fuel consumed in one hour in units of pounds. To convert this to gallons, divide by the weight of gasoline in lbs per gallon which is about 6 to 6.2 lbs per gallon.
 
I HAD A FACET PUP FAIL...TIME TO UPGRADE. JUST SPENT 1 HOUR ON THE PHONE WITH HOLLEY.. NONE OF THEIR PUMPS WILL LIFT FUEL. ANYONE KNOW OF AN ELECTRIC FUEL PUMP THAT WILL LIFT FUEL? 347 WITH WEBERS 470HP.

THANK YOU IN ADVANCE
 

bryanf

Supporter
I HAD A FACET PUP FAIL...TIME TO UPGRADE. JUST SPENT 1 HOUR ON THE PHONE WITH HOLLEY.. NONE OF THEIR PUMPS WILL LIFT FUEL. ANYONE KNOW OF AN ELECTRIC FUEL PUMP THAT WILL LIFT FUEL? 347 WITH WEBERS 470HP.

THANK YOU IN ADVANCE
I've had good luck with the Carter P4600HP.
 
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