D. MAIN METERING SYSTEM - At cruising speed, the fuel flows from the float chamber through the main jet, which measures or meters the fuel flow into the bottom of the main well. The fuel moves up the main well past the main well air bleed hole in the side of the well. The mixture of fuel and air moves up the main well and passes into the short horizontal passage leading to the main body, then through the horizontal channel of the discharge nozzle. This fuel is discharged into the booster venturi and then in the air stream of the carburetor venturi. Filtered air enters through the main metering air bleed in the main body and then into the main metering body by interconnect ing passages. This mixture of fuel and air, being lighter than raw fuel, responds faster to any change in venturi vacuum and vaporizes more readily when discharged into the air stream of the venturi. The throttle plate controls the amount of fuel air mixture admitted to the intake manifold, regulating the speed and power output of the engine in accordance with accelerator pedal movement.					diaphragm at idle or normal load conditions, is strong enough to hold the diaphragm closed, and overcome the tension of the power valve spring. When high power demands place a greater load on the engine and manifold vacuum drops below a predetermined point, the power valve spring over comes the reduced vacuum, opening the power valve. Fuel flows from the float chamber, through the valve and out the small holes in the side of the valve through the diagonal restrictions in the main metering body and then into the main well. In the main well, the fuel joins the fuel flow in the main metering system, enriching the mixture. Some models have an additional very small drilling that leads directly from the float chamber to the power valve cavity. This small hole conducts enough fuel to prime the power valve so that there is no lag waiting for fuel to fill the cavity when the valve opens. As engine power demands are reduced, manifold vacuum increases. The increased va cuum acts on the diaphragm, overcoming the tension of the power valve spring. This closes the power valve and shuts off the added supply of fuel which is no longer required.
E. POWER ENRICHMENT SYSTEM - A vacuum passage in the throttle body transmits manifold vacuum to the power valve chamber in the main body. The power valve which is located in the main metering body is affected by this mani fold vacuum. The manifold vacuum acting on the
					F. CHOKE SYSTEMS - The choke system permits a richer fuel-air mixture which is requir ed for starting and operating a cold engine. Most of the vaporized fuel condenses to a liquid on contact with the cold surfaces of the intake mani fold. In this liquid form it burns too slowly and incompletely in the cylinders and will cause stall ing and loss of power. The choke plate which is operated either manually or by some automatic means may be closed during the cranking period and partially opened during the warm-up, confining manifold vacuum below the choke plate. The greater vacuum causes both main metering system and idle system to discharge fuel into the cylinders.
					(1) MANUAL CHOKE - During the full choking period, the choke plate or plates are held closed and the high point of the fast idle cam is in contact with the throttle stop screw and engine rpm will be higher on starting. As choking is manually decreased, the high point of the cam moves rota tionally away from the throttle stop screw and allows the engine to resume its normal idle speed setting. Other manual choke systems operate only the choke plate. Some manual choke plates may include a spring loaded poppet valve or may have a spring loaded choke plate. After the engine has reached normal operating temperature, the tem perature of the intake manifold will be high enough to prevent condensation and choking will no longer be necessary.
	Power Enrichment System