Exploded Views and Diagrams (Monojet)
Power Enrichment System (Monojet)
Accelerator Pump System (Monojet)
The Monojet carburetor is a single bore downdraft carburetor using a triple venture in conjunction with a plain tube nozzle.
Fuel flow through the main metering system is controlled by a main well air bleed and a variable orifice jet. A power enrichment system is used to provide good performance during moderate to heavy acceleration and at higher engine speeds.
The idle system on all models incorporates a hot idle compensator (AT only) to maintain smooth engine idle during periods of extreme hot engine operation.
The model 1ME incorporates an integral automatic choke system which uses and electrically heated choke coil. The vacuum diaphragm unit is mounted externally on the air horn and connects to the thermostatic coil lever through a connecting line.
The electric choke coil is contained in a choke housing mounted on a bracket attached to the float bowl.
An integral, pleated-pwper fuel inlet filter is mounted in the fuel bowl behind the fuel inlet nut to give maximum filtration of incoming fuel. A check valve on light duty emissions is used in the filter inlet to prevent fuel draining from the fuel system after roll-over.
To improve hot engine starting and meet evaporative emission requirements, fuel vapors from the carburetor bowl are vented to the vapor canister. A tube is added to the air horn to connect air horn and canister.
Other features of the Monojet carburetor include an aluminum throttle body for decreased weight and improved heat distribution and a thick throttle body to bowl insulator gasket to keep excessive engine heat from the float bowl.
On high altitude models, seals have been added in the float bowl to seal the power piston drive rod and the pump lever to prevent escape of fuel vapors to atmosphere. During unit repair, the seals and retainer, where used, must be removed prior to immersion of the float bowl in carb cleaner.
An electrically operated idle stop solenoid is used on all models.
Dual throttle return springs are used on all carbs. The throttle lever has a spun-in plastic bushing, this is used as the bearing surface for the dual throttle return springs.
An exhaust gas recirculation system (EGR) is used on light duty emission and heavy duty emission 454 CID California carbs to control oxides of nitrogen. The vacuum supply port necessary to operation the recirculation valve is located in the throttle body and connects through a channel to a tube which is located at the top of the air horn casting.
Six basic systems of operation are used: float, idle, main metering, power enrichment, pump, and choke.
The Rochester Monojet (often referred to as the 1MV) is a single-barrel carburetor that was commonly used on many GM vehicles in the 1960s and 1970s, particularly on six-cylinder engines and some smaller V8s.
When it comes to its CFM (cubic feet per minute) rating, the Rochester Monojet typically falls in the range of 170-190 CFM, depending on the specific application and configuration. However, it's essential to note that CFM ratings can vary based on the specific engine requirements and tuning.