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

Carburetor Percolation

Percolation can happen when your engine gets hot, then you turn the engine off and the fuel boils over, sometimes over the top of the carburetor, or more often, simply evaporates. Back in the day we called this vapor lock, which simply meant that the fuel turned to vapor before getting to the engine.

This has been a more common problem these days because our gas has a lower boiling point than it used to. Yup you guessed it, ethanol.

This makes it hard to start the next time. You have to crank and crank, or pour a bit of gas down the carburetor to get the engine started.
What can you do:
  • One of the best ways, but a lot of work, is to run a 3rd line from the fuel pump back to the gas tank. This extra line will help cool the fuel, allowing the fuel pump to pump gas instead of vapor. There are some fuel filters out there that include a return port. There are also return regulators available.
  • Put heat wrap around the fuel line in the engine compartment.
  • Put a spacer under the carburetor mount. These are hard to find so you will probably have to make one. Yup, a mill would be handy about now. And you will probably need to put longer studs in the manifold to accommodate the extra height.
  • Instead of a spacer add extra mounting gaskets. A couple of 1/32 thick gaskets isn’t going to do much. Hopefully thicker gaskets will be available for your engine.
  • Add a helper electric fuel pump. Just before startup, you run the electric pump for a few seconds, then turn it off. Use only a low pressure pump. 7 lbs max. You may end up also adding a regulator because you don’t want the pump to overrun your mechanical pump. Most 1 & 2 bbl carburetor run 4-4.5 lbs. Bigger carburetors might handle 5-6 lbs.
  • Cool the engine with a cooler thermostat, bigger fan, or bigger radiator.
  • Try different brands of gas. Different octanes won’t help you here.
  • Use non ethanol gas if you can find it.
  • Remember when we used to put wooden clothes pins on the fuel line? The clothes pins act like a heat sync, drawing heat away from the fuel line and my wife says the wooden clothes pins are still available at the dollar store.
Anyhow, the basic answer here is to cool your engine and/or fuel.




  1. How a Choke Works Integral Type 5 Replies
  2. Motorcraft 4300 Power Piston 1 Reply
  3. Gas Tank Fuel Gauge Leave a reply
  4. Tips on Removing Frozen Parts Leave a reply
  5. Stromberg WW Worn Throttle Shafts Leave a reply
  6. Late to the Electric Party Leave a reply
  7. O2 Sensors – Engine Performance from a Capsule Leave a reply
  8. What Kind of Fuel Mileage Can We Expect Leave a reply
  9. Injector Types Leave a reply