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A mechanical fuel injection system from Hilborn includes the manifold, nozzles, barrel valve, and hoses. The main jet, housed in the primary bypass valve, is also included along with 2 additional jets, or pills. To complete the system, you will need ram tubes, fuel pump, fuel filter, fuel shutoff valve and, possibly, a hi-speed bypass valve. If Hilborn cannot supply a fuel pump drive, you will need to fashion a drive for the pump to run at 1/2 crankshaft speed.
Using your supplied engines specs, racing venue, car characteristics, etc., we will flow the entire system. This provides a very good starting point but tuning will be required to optimize the injection system. A mechanical system is really quite simple, but needs to be tuned to the current weather conditions.
There are 4 main parts to a mechanical system:
Since this is a constant flow system, fuel is supplied to the engine continuously. As the pump spins, the restriction in the system (set by the nozzle and main jet) develops pressure and, therefore, fuel flow to the engine. The nozzle size is picked to deliver enough fuel at WOT for your engine, while the main jet is used to adjust the amount of fuel allowed to return to the tank, setting the actual fuel curve. This is exactly opposite of a carburetor. The barrel valve acts like a fuel shutoff, controlling the amount of fuel for idle and transitional fuel to WOT. The barrel valve also works in conjunction with the secondary bypass valve for better part throttle fuel control. At higher RPM the fuel pump will produce more pressure and volume than the engine can use, so a hi-speed bypass (or cutoff) is required.
These operating tips and suggestions are the result of experience gained by years of running under varied conditions.
Set injector to wide open throttle. As pictured in the Metering Valve Schematic, the distance “X” between the center of the rod-end bearings is equal to the distance “Y” between the center of the throttle shaft and the center of the metering valve rotor (#54 shown). Note that the inlet fitting on the block is off-set to one side. Adjust the rotor so that the number is located on the wide side of the off-set. Tighten arm on the rotor and the throttle shaft.