Rochester 4G, 4GC Carburetor


Also known as the 4 Jet carburetor.

Rochester 4G, 4GC Carburetor Manual

Watch a video about the accelerator pump vent.

Watch a video about rebuilding the Rochester 4 Jet.

Watch a video about the Rochester 4GC integral choke.

Watch a video about the Rochester 4G jets.


Can one of the emulsion tubes be missing from the venturi?

Sometimes those fall out.  I would simply try to find another 4G and pirate an emulsion tube from its booster cluster.  Compare the size/number/placement of holes with the remaining tube and modify as necessary.  Install new tube to same depth as old one with a light coating of Permatex Anaerobic Gasket Maker on the press-fit surface.


When I took apart my 4gc (7024121) there was no aluminum check ball in the pump intake cavity. Does it take the large one or the small one that is in my kit?


1st you have to be sure you need a check ball. Carburetors that use a check ball in the accelerator pump well will have two holes at the bottom. One for intake and the other for out flow. When there is only one hole, then no check ball is needed since the hole is the out flow and if you placed a check ball there, the flow to the main discharge would be cut off. When you have two holes, then use the smaller of the check balls and these are often made of aluminum instead of stainless steel. Aluminum is used to make the check ball lighter since only the weight of the fuel lifts the check ball off of the hole to allow fuel to enter.

9 thoughts on “Rochester 4G, 4GC Carburetor

  1. Hello Mike, I just rebuilt a 4gs off a 59 Olds Super88 (sorry found your site only after purchasing another kit), but have trouble setting the float level, because there is a spring loaded cup at the end of the power piston and the fork which controls the position of the floats rubs on the cup – making it not unique as far as the float level goes. It can settle at various levels, when I hold the power piston all the way up. Your carb does not seem to have this in the video, any advice? The car runs ok but cuts out when cruising constant speed or going uphill, ok under load and acceleration – already replaced the fuel pump, dropped tank and replaced leaky fuel hose, with no significant change.
    thanks much for any advice

  2. hi mike. harry here from emerald city automotive in Gaithersburg md. I have a problem with the accelerator pump on a 63 chevy 327 4gc carb . there is no inlet checkball on this carb. the pump will not squirt until it is almost to the bottom of its bore.(has off idle hesitation) how does this carb even get fuel into the pump bore ? and what can I do to make this carb pump work properly? thanks in advance, Harry

  3. I have a rochester 4 jet on a 1961 chevrolet with the 283, there is no tag or numbers on the carb. Having trouble with hesitation and have rebuilt twice. What is the correct accelarator pump I should be using? The one in it is 2 5/8 mlong with 5/8 cup,

  4. I need help to identify a carter carb on a 1960 biscayne,the engine decodes back to 1958 283,it looks like a regular carter carb but has a wierd attachment on th passenger side ,a counterbalance weight and has a additional butterfly on the secondary any clues?

  5. Hello Mike.

    Can you tell me where I can find a Carter W1 Carb Governor??. I have a 1946 Chevy 1-1/2 Ton, Flatbed Truck.
    What is the part number, What does it look like, And where can I find one??.

    Thank you for your time..

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