OK, so how do we figure what electric fuel pump to use? Now this is essentially related to using an electric fuel pump by itself, but it can also let you know if the factory stock mechanical fuel pump or if one of the aftermarket mechanical fuels pump will work for your build. Keep in mind that there are replacement gas tanks, and even retro-fitting kits, that allow an in-tank electric fuel pump. The prices on some of these set-ups are not too bad if you need to replace your tank anyway - and some have baffles to prevent fuel starvation on those hard launches. So again, you have options on how to go, but the important part is fuel pump GPH flow based on the HP requirements of your engine build - so this is loosely a guideline that can be used.
Choosing the Correct Fuel Pump
Different fuel pump manufacturers rate their fuel pumps in different ways. Some manufacturers for instance rate their fuel pumps at free flow. The problem with this rating is that no fuel system operates at zero psi. Other fuel pump companies may rate their fuel pumps at a given psi. For example the Walbro fuel pumps that we sell are rated at 40 psi. Our most popular fuel pump we sell is the 4 series fuel pump assembly. These assemblies use a Walbro 255 lph fuel pump. 255 liters is the volume of fuel that the pump will flow at 40 psi. While this is a more accurate rating than a free flow rating, the 255 lph rating is only accurate if you are running your engine at 40 psi and your pump is being supplied with 13 volts.
Sometimes pumps are rated based on pressure. For example the Walbro 255 lph pump is capable of producing a pressure in excess of 100 psi. While this information may be relevant, it only provides one detail about a fuel pumps capability.
The better way to select a fuel pump to use in your fuel system is to consider three factors:
How much horsepower your engine will produce.
What fuel pressure is required for your engine.
How much voltage is supplied to your fuel pump when the engine is running.
The amount of horsepower that your engine has will determine how much fuel flow is required to support that engine. As horsepower increases so does the volume of fuel required to support that power. A good estimator of volume to power is approximately 10 hp per gallon or 2.64 hp per liter. For example if your pump flows at 50 gph it should be able to support a 500 hp engine (50 x 10 = 500). However, to actually know the gph you must also consider the fuel pressure required for your engine.
2. Fuel Pressure
Different engines require different fuel pressure. For example a carbureted engine typically requires between 4 to 7 psi.
It is important to know what the max pressure your engine will require because fuel pressure has a large effect on how much flow a pump can produce. A fuel pump will flow at its highest volume when there is no pressure (free flow). As fuel pressure increases, fuel flow decreases. Every pump has a different flow volume at a given pressure. Because of this it is important to look at a flow chart of whatever pump you decide to buy. As free flow, or even flow at a given pressure is only part of the equation.
Fuel pumps have different flow rates at different voltages. As voltage increases so does the speed of the fuel pump which will increase the flow of a pump at any given pressure. Because of this it is good practice to see how a pump is rated at a given voltage. Most cars will produce about 13.5 volts when running. However, if your alternator does not produce 13.5 volts, or you simply want to plan conservatively simply look at the flow ratings of a pump at 12 volts.
Info from: Choosing the Correct Fuel Pump
Feeding a Carbureted Engine with an EFI Fuel Pump
It is becoming more and more common for people to use an in-tank electric pump to feed a carbureted engine. Many new engines simply do not have the provisions to use a mechanical fuel pump. Sometimes there is no room to have a mechanical fuel pump in the engine compartment. Others simply want to clean up the look under the hood and do so by removing the mechanical fuel pump.
Any of our in-tank pumps can feed a carbureted engine provided that a bypass regulator
is used. Because an EFI fuel pump can produce a large amount of flow, a bypass regulator is necessary
in order to return the excess fuel back to the fuel tank. When shopping for a bypass regulator make sure that you buy one that is specific for carbureted applications. This is because most carburetors only require around 6 psi to operate. Typical EFI bypass regulators run between 40-80 psi while most carbureted bypass regulators are adjustable from 4-10 psi. Keep in mind that since the pressure requirements of a carbureted application is lower that an EFI application the flow rate of your pump will be higher. This means that the fuel pump is capable of supporting higher horsepower. For most applications our TBI or 2 series fuel pumps provide enough flow for a carbureted engine.
Info from: Feeding a Carbureted Engine with an EFI Fuel Pump
The Aeromotive 13301 Bypass Fuel Pressure Regulator
, 3-60 PSI Universal Fit, Gasoline Fuel Type is one option in using a bypass regulator when using a high pressure electric fule pump. https://www.speedwaymotors.com/Aerom...PSI,40596.html
Here is a kit that uses an Edelbrock brand
Bypass Fuel Pressure Regulator, Fuel Line Kit for Carbureted Engines with Bypass Regulator
The Aeromotive piece has 3/8" outlets which I have read is clost to AN-8 size and what you typically want and would work with our GTO's 3/8" gas line. The Tanks, Inc set-up uses the smaller AN-6 size lines & fittings and may work better with those earlier GTO's with 5/16" gas lines. In either case, a little research would be needed in meeting your gas line size requirements. The key here I believe would be how many gallons per hour your engine needed and how many gallons per hour either the 3/8" or AN-6 lines/fittings can provide.