Nitro Type Metering Valve
The idle check valve should be installed where the housing is marked "RET". The upper check valve is the high pressure pump relief and should also have a return line. The fuel line from the pump should be connected to the fitting marked "IN". The line to the port nozzles should be connected to the fitting marked "PORT".

Methanol Type Metering Valve
The idle check valve should be installed where the block is marked "OUT". Connect the return line to this check valve. The fuel line from the pump should be connected to the fitting marked "IN". The fitting in the rear corner of the metering valve should be connected to the top nozzle distribution block. Systems utilizing port nozzles will have an outlet fitting installed in the bottom of the metering valve.

Idle Control
The idle mixture is controlled by the turnbuckle on the side of the injector. To richen the idle, rotate the turnbuckle towards the rear of the injector, (shortening the linkage leans the mixture, lengthening richens the mixture). This adjustment is for idle and throttle response only and has no effect on full throttle. The idle speed is controlled by the butterfly shaft stops on each side of the injector.

Main Bypass Pill
Each Enderle fuel injector is furnished with a set of bypass pills. This bypass controls the fuel mixture at full throttle and has little or no effect on the idle. The bypass pill is located under the 9/16 hex plug on the metering valve. Use a smaller bypass to richen the fuel mixture and a larger bypass to lean it. When installing the bypass, make sure that it is seated at the bottom of the threads.

High Speed Bypass System
Certain applications require the use of a hi-speed lean out. This consists of a bypass pill controlled by a high pressure check valve which leans the fuel mixture at high RPM. The check valve pressure is adjusted with shims to tailor the fuel curve to the engine’s requirements. The check valve opens when the fuel pressure is able to overcome the spring tension. The bypass pill controls the volume of fuel returned. Adding shims will make the check valve open at a higher RPM. Removing shims will make the check valve open at a lower RPM. The hi-speed should be thought of as a fine tuning device. The main bypass pill is the primary control of the overall fuel mixture.

Maintenance
The fuel system should be drained between races. It is important to lubricate the fuel pump with Prolong SPL100 or some other type of similar lubricant. Remove the inlet line from the metering valve and lubricate the metering piston to prevent stickiness and drying out.

You must use a 3-way fuel shutoff with a return. A 2-way style shutoff may damage the fuel pump.