Rochester Monojet Carburetor

The 1MV monojet carburetor is a single down draft unit using a triple ventuir in conjunction with the plain tube nozzle. The main venturi is 1 7/32″ in diameter and the throttle bore is 1 7/16″.
Fuel flow through the main metering system is controlled by a main well air bleed and a fixed orifice jet. A venturi velocity power enrichment system is used to provide good performance during moderate to heavy acceleration and at higher engine speeds.
An exhaust gas recirculation, E.G.R. system controls oxides of nitrogen emissions. The E.G.R. valve is operated by a vacuum signal taken from the carburetor throttle body.
A vacuum supply tube installed in the carburetor throttle body connects by a passage to timed vertical ports located in the bore of the throttle body and float bowl. The ports provide a vacuum signal to the E.G.R. valve in the off idle and part throttle operation of the carburetor.
The E.G.R. valve, mounted on the intake manifold, circulates a metered amount of exhaust gases to the combustion mixtures to lower peak combustion temperatures, thereby reducing oxides of nitrogen during these ranges of engine operation.

The E.G.R. system is not in operation during the engine idle.

A pleated internal paper fuel inlet filter is mounted in the float bowl behind the fuel inlet nut to give maximum filtration of incoming fuel.

The carburetor has an aluminum throttle body, a thick throttle body to bowl insulator gasket, and a internally balanced venting through a vent hole in the air horn which leads into the bore beneath the air cleaner. The float bowl is externally vented under extreme conditions through a pressure relief valve system.

The carburetor part number is stamped on vertical section of float bowl, next to fuel inlet.

An idle stop solenoid is used to control idle. The solenoid is electrically  controlled through the ignition switch. When the ignition switch is tunred off, the solenoid is denergized, allowing the carburetor throttle valve to close further, preventing the engine from running after the ignition switch is turned off. On manual transmission models, the  solenoid also deenergizes when the clutch is disengaged.

Rochester Monojet Identification

Monojet Identification

1980 Monojet 1ME Exploded View & Parts List

1981-85 Monojet 1ME Exploded View & Parts List

1985 & Later Monojet 1MEF Exploded View & Parts List

Float Level Adjustment

Monojet Float Level

Fast Idle Cam Adjustment

Monojet Carburetor

Vacuum Break Adjustment

Monojet Carburetor

Choke Coil Lever Adjustment
Quadrajet Adjustment

Trouble Shooting the Monojet M MV Carburetor

Adjust the Idle Mixture

Recent Posts

Holley 1920 Floods Coming to a Stop

After running my vehicle and I turn it off, gas floods over into the intake flooding the engine. Won’t start.

  • Could be fuel pressure – When the engine if shut off there should be some release of pressure. Make sure you have a vented gas tank. After running open the gas cap. Do you get a rush of air? If so, then you need to vent your gas tank. Some vent through the gas cap itself and some have a separate tube coming up from the gas tank. Make sure the tube is clear. Test your fuel pressure. Should be about 4 lbs or less, but compare with what your motor manual says.

Holley 1920 Flooding

  • Your gas may be percolating – The engine gets hot, you turn it off and the gas boils over, or evaporates out of the carburetor. Gas has a lower boiling point these days and especially in hot parts of the year, this may be a challenge. Experiment with different brands of gas. Try Startron ethanol additive in the gas. Make sure fuel lines are away from the manifold. Is your water running at a good temperature. While very hard to find, spacers will sometime help. Do you have a bowl vent on top of the carburetor and is it hooked up to a hose correctly? Check the bowl vent gap. Specifications are in the carburetor kit instruction sheet.

Holley 1920 Flooding

  • Some Holley 1920 carburetors have a hot idle compensator. The compensator opens a vent into the main body letting off some pressure when coming to an idle. If the idle compensator is bad the idle will be erratic. To test:
    • Remove the air cleaner with engine running.
    • Cover the hot idle port. If the idle smooths out there is something wrong with the idle compensator. Check the seal and/or replace.
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