Rochester Carburetor Parts. Carburetor Doctor carburetor rebuild kits, floats, choke pull offs, choke coils and other parts for Rochester carburetors are here. We have ethanol-compatible parts for all Rochester carburetors from the first Model AA carburetor in 1949 to the computer-controlled QJets of the 80's and on to aftermarket Edelbrock Quadrajets and marine carbs. How to Rebuild and Modify Rochester Quadrajet Carburetors by Cliff Ruggles is a frequent recommendation by the members of Hotrodders forum. It is a highly-reviewed book and the author is considered a leading authority on Quadrajet carburetors. Product Description. Professionally remanufactured Rochester Quadrajet Marine carburettor providing optimum performance and best fuel economy. The carburettor has been completely remanufactured in house and consists of new gaskets, needle and seats, new bushes on shafts, all screws and shafts have been replated and the carburettor is hot run tested upon completion.
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Carburetor Technical Information
Rochester Quadrajet
Quadrajets were used as original equipment on many vehicles from 1965 to 1990. Over 100 million have been produced.
1966 Rochester Quadrajet used on 327 Chevrolet engine with manual transmission, no. 7026203 - number is on the blue 'bottle cap' visible on the throttle side
Design
The QJet is a large 4 barrel carburetor that has a small primary side for fuel economy and good emissions and a large secondary side for good performance. QJets have a maximum airflow of from 750-800 cfm. Because the secondary side of the Qjet opens according to the airflow requirements of the engine, the same basic carburetor size can be used on a large range of engine sizes. The basic 750 cfm QJet casting is used from 231 CID to over 400 CID - the big secondary air valves open only as the engine breathes. For example, on a mild 350 Chevy the air valve will never open all the way - because the motor can't use more than 600 cfm or so.
1980 Chevrolet truck Quadrajet, M4MC type (hot air choke), no. 17080213.
M4MC Quadrajets have an integral choke and a different airhorn design; also, the throttle shafts are longer than in 4MV carbs. Starting in 1968 carb numbers were stamped on the driver's side, near the back.
Identification
There are three basic types of QJet: the original 4M (starting in 1965), M4M (1975 onward) and E4M (from 1979). All QJets had automatic chokes, of which there are two basic types - integral (choke coil on the carb) and remote (choke coil on the manifold). 4MV carbs have the choke coil on the manifold and 4MC carbs have it on the side of the carb in a housing. An M4MC carb has a choke coil on the carb; and M4ME carb has the same type fo choke coil, but with an electric heater element in the choke coil.
Choke parts, primary metering rods and throttle shafts are not interchangeable between 4M and M4M carbs.
Rochester Quadrajet Rebuild Manual
Oldsmobile M4MC Quadrajet carburetor, showing the front fuel inlet used on BOP (Buick-Olds-Pontiac) carbs
Rochester Quadrajet Manual
Evolution
Marine Rochester Quadrajet Replacement
- 1965-66 4MV, 4MC: hydraulic piston damped air valve; originally came with diaphragm-type fuel inlet valve - now upgraded with needle/seat type; 4MV (remote choke) used on Chevy starting with 1965 396; Oldsmobile used the 4MC on Toronado in '66
- 1967-1971 4MV, 4MC: vacuum break used to damp air valve instead of piston; fuel inlet thread is 7/8'-20 on most carbs
- 1972-1979: 4MV carbs are used on cars until 1974; trucks until 1979; fuel inlet thread changed to 1'-20 in '72
- 1975: M4MC carbs have different metering rods from 4MV and have a carb-mounted choke; used on passenger cars and some trucks from 75-up
- 1980: E4ME computer controlled carb
- 1985: M4MED electric choke carb with dual capacity pump solenoid used on Federal trucks and various Canadian vehicles
- 1985: M4MEF with adjustable secondary air bleeds used on 454's with HD emissions, E4MED and E4MEF in California
- 17088152: the last automotive Quadrajet number (an E4ME)
- 17089112: the last Rochester Quadrajet number - a 4MV used on Mercruiser 502 MAG engines