Setting up the fuel system is likely the most challenging part of a carburetor to EFI conversion. If you are considering producing any significant amount of power you'll want to redesign the entire system, with proper EFI components and fuel lines sized to your anticipated power level. It's in the proper selection of fuel system components, rather than the installation, where the complexity lies. Mass-Flo now also sells complete fuel systems using the same Mallory components we used here.

How Much Fuel?
Picking up a parts catalog and ordering a fuel pump, injectors and other components solely on the claimed supported power levels is surely to result in a costly mismatch of parts. You have to begin with some calculations. The first step is to determine how much horsepower your fuel system needs to support. This should be a realistic figure representing flywheel horsepower. The good thing about EFI systems is that it is ok to have a system which supports more power than you may be making, within reason. If your motor is at 400 horsepower now but you are planning for a supercharger, use 600 HP as the value.
The next variable needed for the equation is BSFC or brake specific fuel consumption. Without the proper dyno cell and measuring equipment it is not practical to actually calculate BSFC. However, engineers have determined BSFC to be between 0.4 and 0.5 for typical four-stroke naturally aspirated gasoline engines. Use a value of 0.6 for nitrous and 0.7 for forced induction. Multiply your engine horsepower by the BSFC factor to get fuel consumption in per hour. We've calculated that a 600 horsepower supercharged car would need 360lbs per hour. A gallon of pump gas weighs roughly 6lbs, so this equates to 60 gallons/hour, or 227 liters/hour (1 gallon = 3.79 liters.)

So we should go out and get a 60 gph pump right? No. The volume that a pump puts out is a function of pressure. Therefore we cannot simply rely on the advertised free-flow fuel pump volume ratings. We need to select a pump that will flow at least 60 gph (227 lph) at 40 psi, the psi of our fuel injected system. For our 600HP example application the Mallory 5110FI Comp Pump would be ideal. According to Mallory's flow data this pump will produce 90 gph at 40 psi, well above our requirement of 60 gph. Alternatively the Mallory 4261FI universal pump is rated at 226lph (60gph) @ 40psi. This pump would be right on the border line of our fuel requirement and probably better suited for a 400-500 horsepower application. For our project we'll start off with the easy-to-install universal inline 4261FI pump. Once we have the engine running and tuned naturally aspirated we will then install a Vortech supercharger and upgrade to the 5110FI pump. Look for this in part 2 of this series in an upcoming issue.

Injector Sizing
Once you have calculated the amount of fuel your engine would use, in pounds per hour, you can easily calculate the proper injector size. This is done by dividing the fuel requirement by the number of injectors (8 for a V8 engine, etc.) In our example of 360 lbs/hr this gives us an injector size of 45lbs/hr. However injectors should not operate at 100% of their "duty cycle". Duty cycle is the time the injector is open before it must open again. At high rpm duty cycle should not exceed 80% to avoid overheating and damaging the injector. Therefore we want to divide our result of 45lbs/hr by 0.80 to give a safety factor. This yields an optimal injector size of 56 lbs/hr for a 600 horsepower engine. We will initially start with a set of 30lb/hr injectors to get the EFI system up and running naturally aspirated. When we install the supercharger we'll step up to the larger fuel pump and injectors.

We had previously modified our stock fuel tank pickup to 1/2" line and welded on a -8AN fitting. This will make it easy to plumb in an external EFI fuel pump.	We mounted the Mallory 255lph inline fuel pump above the fuel tank, screwing into the trunk sheet metal and not the tank! We're using the Mallory filter to keep the pump clean of debris.
The Mallory 3175 fuel filter comes with a 40 micron disc filter. This is sufficient as a pre-filter for the pump, but not as a filter for fuel injectors. We'll mount another filter in the feed line before the injectors and use a 5 micron element, available from Mallory PN# 3177.	The 1/2" aluminum hardline runs from the fuel pump, along the subframe connector, and to the front frame rail. Here it connects to another Mallory 3175 filter, this one with a 5 micron filter element to keep the injectors clean.
Saftey is of utmost importance with any fuel line, but more so with the high pressure EFI lines. Rather than pass a hose through sheet metal we're using an Aeroquip bulkhead connector. Available in various AN sizes and angles this also preserves our -8AN feed line to the injector rails.	The injector rails get -AN to NPT adapter fittings. Use Teflon pipe sealant (not tape) on only the pipe thread side of the fitting, never use any sealer on the 37° taper or AN threads.
From the bulkhead fitting at the firewall the fuel enters the driver-side injector rail. A short piece of hose routes the fuel to the passenger side rail and then out to the regulator.	There are several ways to configure the regulator. We have a single -8AN line from the rails to the regulator. Alternatively each rail can have separate feeds and exit lines to the regulator. In all cases you must run a bypass (bottom fitting) which returns the excess fuel back to the tank. We're using a -6AN return line.
The easiest way to get fuel back into the tank is to modify the fuel filler neck. We pulled it out and welded in a steel bushing which we tapped to accept a -AN fitting. Don't make the mistake of welding the fitting to the tube because you wont be able to get the tube back through the tail light panel.	Our aluminum return line runs under the car and then is coupled through the trunk floor with a soft line that routes the fuel to the tank via the filler neck.
Don't wait until you are ready to fire up the car to test the fuel system. We threw in a few gallons of fuel and wired the pump directly to the battery to prime and check for leaks.	The system showed no leaks and we verified pressure. This is also a good moment to set the initial fuel pressure to 39 psi. Once the motor is running you can set it to 39 psi with the vacuum hose disconnected.

In the next installment of Project '67 you'll see the results of the EFI conversion on our 331 motor. We'll then install the supercharger and tune the EFI system for maximum power. Continue to:Part II - Getting it to Run