Perhaps now you have got whiff of the idea that if you can add more fuel, you can get a bigger boom. So, why not just dump 500 gallons per hour through the engine and along the way make a couple million horsepower? That would be nice (albeit expensive) but unfortunately this is not the case. Remember, the fuel has to mix with the air, and if there isn’t enough oxygen to mix with all the fuel, then unburned gasoline will be left over. Here’s a quick high school chemistry review. The ideal ration between air to fuel, for a complete and optimal combustions, is 13 parts air to one part fuel. Thus 1 gallon of fuel needs to mix with 14 gallons of oxygen to ignite and provide maximum power. So for the case of an internal combustion engine, air is the limiting factor in making horsepower.
OK, enough science talk. What does this actually mean in terms of your Mustangs fuel system? Let’s go over the stock setup real quick. Out of the factory, 1987-1993 5.0 Foxbodies all came with an in-tank electric fuel pump rated at 88 lph (litres per hour) that would send fuel through the lines up through the regulator and into the fuel rails, where it would be dispensed into the proper combustion chamber via the 19 lb/hr (pound per hour) fuel injectors. The tank itself has a capacity of 15.4 gallons (60 litres). All in all, for the stock 225HP engine, this system performs very well, but does not leave much room to grow.
Now, say you are going to be pushing more than the factory 225 ponies, you will need to make a few adjustments to the fuel system to enhance its capacity.