Introduction
With all of the pages dedicated by automotive magazines (FordMuscle not withstanding) to glamorous "air flow" parts such as heads, intakes, cams and power adders, it is easy to forget the fundamentals: It is fuel, not air and not the engine, that contains the potential energy to ultimately move our cars. We can add as much air we want but without the right amount of hydrocarbons, the motor isn't gonna produce a lick more horsepower.

Perhaps one of the reasons we don't see many articles dedicated to fuel system upgrades is that in and of itself installing a new fuel pump or bigger lines will not yeild more power. Most factory fuel systems on V8 Fords are capable of supporting as much as 400 horsepower with minor upgrades. However with those aforementioned air-flow increasing parts making 400HP out of a V8 Ford has become a bolt-on affair, and more and more street cars are eclipsing that mark. Case in point is our Project '67, which put down over 500 horsepower at the wheels with the mere addition of a supercharger. However the engine showed signs of severe fuel starvation with aif-fuel ratios off the charts. Clearly it was time to address the fuel system.

Understanding Volume and Pressure
The relationship between pressure and volume is inverse. In other words, as pressure increases volume decreases. Consider the simple example of a garden hose. If you put your thumb over the end you increase the pressure, but decrease the amount of water that gets past. It is for this principle that simply increasing fuel pressure is not going to get more fuel into the motor. We have to consider the volume requirements of the motor.

Engineers have termed the volume required by an engine as Brake Specific Fuel Consumption, or BSFC. BSFC is the amount of fuel (in pounds) required to make one horsepower for one hour. A typical naturally aspirated street engine has a BSFC of 0.5, meaning it will consume one-half pound of fuel per horsepower per hour at wide open throttle. The BSFC goes down as engine efficiency rises. BSFC tends to go up with super and turbo chargers as they are not as efficient.

For our purposes BSFC is a theoretical value. Without the proper dyno cell and measuring equipment it is not practical to actually measure BSFC. Engineers have determined BSFC to be between 0.4 and 0.6 for typical four-stroke gasoline engines. Using a value of 0.5 lbs per hour per HP (or 0.6 for a blower car) will get you on the right track. We can use this number to calculate how much fuel a motor will need if we know the maximum horsepower it will produce. Multiply your engine horsepower by the BSFC factor to get fuel consumption in pounds per hour. We've calculated the requirements for a 600 horsepower supercharged car:

The results above show that to run a 600HP motor at WOT for a continuous hour would require 60 gallons of fuel (pump gas weighs about 6lbs per gallon.) When selecting a fuel pump we want to look for adequate gph rating at the fuel pressure we will be operating. However in this case if we used a 60gph @ 8psi fuel pump our motor would surely be starved for fuel because this is a nominal rating. In a real fuel system and real vehicle there are other factors which add to the fuel pressure. The diameter of fuel line, the g-forces upon launch, pressure from boost, etc. As a result we must factor in a safety margin. A Carter mechanical "strip" pump, rated at 140gph will flow somewhere in the range of 100 gph with 12psi of fuel pressure. This would be a more appropriate fuel pump.

A word on Regulators
A fuel pressure regulator is used to reduce system pressure into a specific range for the carburator or fuel injector to meter properly. Regulators come in two varieties, dead-head and return style. A dead-head regulator works by maintaining a lower pressure down stream (between regulator and carb or injectors) by blocking higher pressure behind it via a diaphragm and spring. A return-style regulator uses a bypass and a separate return line to bleed off excess fuel and return it to the tank. Dead head regulators work fine for low pressure mechanical fuel pumps because the excess pressure against the fuel pump is over come by crank power. However electrical fuel pumps, especially high-output EFI pumps, will run hotter and less efficiently if they are pushing against a dead head regulator, therefore it is best to use a return style regulator with these pumps.

Planning it out
Once you have figured out the fuel pump requirements based on your horsepower level the next step is to plan out the pumbing. It is important to select fuel lines that support the pump rating. A big pump with small lines will result in too much pressure and the pump will not deliver the rated volume. The pump also must receive adequate volume from the tank so it does not cavitate (suck air.) The next two pages show how we modifed the pickup unit and fuel lines.