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


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Mustang You Gotta Love

Here is an interesting story from one of my customers. We were discussing some of the problems he was having with his Motorcraft 4300 and shared his story with me.

mustang 1

These 4300s did run for some people, at least a mile or two off the lot. When the carb didn’t flood, I really enjoyed the heck out of it. Dad got the ‘Stang from the original owner in ’85 – a nurse who drove it back and forth to work since she started college in ’68. I started working on the car when I was 18 and a novice. Back then you could find interesting random things in the boneyard, even if you had no idea what they were. Every time I saw something different in the junkyard I bolted it on the car. I had no idea what I was doing back then AT ALL so I scrounged around in the busted metal and replaced the Autolite 2100 carb with the aforementioned “Frankenstein” 4300 (unconsciously amalgamated from several T-Bird & Falcon carbs), an intake manifold off a ’66 4-bbl. Mustang, the rear anti-sway bar off a Boss 302, the tall 4-bbl carb spacer off a ’64 Galaxie, the Cyclone headers and fat dump-off exhaust pipes off a Boss 351 as a complete set out of a guy’s garage for $40 back in ’89, and here I am at almost age 50 still with good vision and reflexes with actually still a matching # car if I pull the parts out of the attic except for the original 2-bbl carb which burned up in a 2011 shed fire. And the VIN-matching engine has 164K miles, heads rebuilt by original owner at 70K, and I have flogged it like a rented mule for 30 years come September, with only one C4 rebuild in ’88 and good compression all around.

mustang 2

Back in the ’80s my brothers crashed it 3 times including a diagonal head-on, and then my best friend took out the entire left side backing up out of his garage without looking. The other brother lost control on a “deadman’s” curve and almost launched it at speed off a cliff into a condo subdivision (because he says the tilt-wheel popped up on him – hmm) but just before shooting into space he swerved and folded up the right-front suspension on the retaining curb like an aircraft landing gear. The best friend also lost control & drove through three front yards and a hedge as I tried to teach him to drive, and before I could yank the key he took out an entire sprinkler system that had just been fabbed, still above ground, because he didn’t understand (!) how to use the steering wheel to straighten the car once turning (!). Bumped over a juniper bush & caromed off a light pole dragging new PVC pipes out into the street – my young cousin screaming bloody murder in the back seat – she is now a college professor – and I found a long sprinkler riser and head lodged in the left coil spring when I got home & investigated the noise.I felt very bad because I knew a lot of work had gone into that front yard. That was long ago and we were so very young –  I was dumb to try to teach my friends and brothers to drive in a 289. But they never bent the frame. Used to do 109 on the 1.02-mile strip on the front side of what later became Louis Zamperini Field airport in Torrance, California (same war veteran that Angelina Jolie made “Unbroken” about) before they built all the auto dealerships on Pacific Coast Highway and trafficked up the area. No cell phones back then and anyway no reaction time – they wouldn’t have helped: We’d have one friend wait at the first stop sign halfway down the one-mile strip and flash a flashlight if a car came and another one at the end of the mile to do the same – if no one flashed you’d blow through the mid-way stop at full throttle (109 was the top speed you could make with the 2-bbl before hitting the T-intersection) and the front end would start lifting up on those old Mustangs, the steering getting skittery-light and at the end if no flash then squeal hard and sideways into the intersection at the T as fast as you dared, about 70mph hitting the stop sign jumping on the disc brakes and smoking sideways wrestling the wheel, flat on the Boss sway bar so that you could record your fastest time at the very end of the Airport-Road run.

mustang 3

I still love ramrodding this survivor car when back in California, hammering hard fast and true, in the desert, snow and open road along the coast. I’ve had snow flying crosswise through the missing windows at 10,000 feet but with the Boss 302 sway bar and the right BF Goodrich T/As (P215-70R14 front, P235-70R14 rear) it handles like a champ and I don’t yet want to give up on the carb problem.

There’s my story – :)

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