K style metering valve

Originally deigned for nitro engines in the 70's ( they used 2 barrel valves), now it is the most common setup for Alky engines
For Alcohol blue is fuel to engine, red is returned fuel, yellow is optional returned fuel. -- Alcohol fuel system components Metering valve ( barrel valve ), Main jet ( pill ) is installed in the metering valve, High speed by pass, Port nozzles, Pump relief valve (most alcohol systems should have them), Idle check valve, 3 way shutoff, Fuel Pump most big cubic inch engines use a 110 fuel pump, some big cubic inch - high boost - high house power engines use a 990 fuel pump. Minimum main fuel line size for alcohol is -16 or 1". Fuel return lines must discharge at opposite end of fuel tank from main fuel line pick up. Fuel tank must be vented.
( Supercharger Fuel Injection Hat delivers air to the system) - ( Metering Valve controls fuel flow to all components ) - ( Main Jet richens or leans total fuel system) - ( Nozzles hat and port spray fuel into air intake system they are jets and come in all sizes ) - ( High Speed By Pass the body holds a jet ( pill ) and has a settable opening psi. check valve)- ( Pump Relief Check Valve allows high psi. fuel to return to tank when throttle is shut has a settable opening psi. ) - ( Idle Check Valve has a settable opening psi.) - ( Port Check Valve has a settable opening psi.) - ( 3 Way Shutoff allows pumped fuel to return to tank when shutoff ) - ( Fuel Pump delivers fuel to the system)
BF-Air The idle speed is controlled by the butterfly shaft stops on each side of the injector opining set engine idle rpm
PS Pump saver - Pump relive check valve set to 150+  psi
Brass #6 check valve
IN Inlet from fuel pump - after fuel shut off  
IDLE set maximum idle pressure - when butterflies are closed  set to 10+ psi
 Brass #6 check valve
MAIN This bypass jet controls the fuel mixture at full throttle and has little to no effect on idle. The bypass pill is located under the 9/16 hex plug on the metering valve. Use a smaller bypass jet to richen the fuel mixture and a larger bypass jet to lean the fuel mixture. When installing the bypass jet make sure that it is seated at the bottom of the threads.

usually .080 - .150

if pump is to large a second circuit is added to the pump called a pump loop, usually a 15 psi check valve and a .100 jet

IDLE-Fuel 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.

This is set with a leakdown tester (build and use your own)

HS some applications require the use of a hi-speed lean out. This consists of a bypass jet 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 engines requirements. The check valve opens when the fuel pressure is able to overcome the spring tension. The bypass jet controls the volume of fuel returned. Adding shim will make the check valve open at a higher rpm. Removing shim  make the check valve open at a lower rpm. The hi-speed should be thought of as a fine tuning device. The main bypass jet is the primary control of the overall fuel mixture.

usually set to 50 - 100 psi
Brass #6 check valve

HS-Jet  from .050 to .100
Hat-Lines they are both common outlets to go to distribution blocks that supply the injectors  
Ports ports have a # 8 check valve set to slightly higher than idle to eliminate dribbling in one cylinder
  To adjust the idle mixture at partial (staging) butterfly opening -  You need to file the width of the small slot in the internal barrel  
pump saver outlet can be routed to blower injector distribution block , so when butterflies are suddenly closed at end of run the excess fuel is dumped into the motor cooling the blower, for a short period of time
Gorr Barrel Valve
the idle mixture is NOT controlled by the turnbuckle on the side of the injector. To richen the idle rotate the first adjusting screw on side of BV, the secound screw is the mixture at partial (staging) butterfly opening. This adjustment is for idle and throttle response only and has no effect on full throttle< but controls the engine temperature at launch.  NOTE - requires #8 idle check valve set to a higher pressure , and is available in different volume ranges
to clean up the fuel system a distribution block can be added to the pump, the check valves can be mounted at BV or at tank or joined in this distribution block, pump loop can be added here also.