At The Old Car Manual Project, we get quite a few questions about technical matters, specifications, historical information and so on.
From time to time I’ll try to answer a few of these here.
Cristobal from Chile wrote:
I have a oldsmobile omega 78′ with a V6 buick 231 engine, and a
rochester carburator 2GE model. I am trying to find the difference
between the 2GE and the 2G, 2GC and 2GV carburators, but i can’t find
it. The only difference that i could see, is that my carburetor uses a
solenoid and no automatic choke. Could you respond this doubt?
I sent you a pictures of the carburetor.
Good question! This is the source of some confusion among Rochester owners.
- 2G is the model of the basic Rochester Two-Jet carburetor with a manual choke (cable operated)
- 2GV is the same carb with an automatic choke when the choke coil is mounted on the manifold (a so-called remote choke)
- 2GC is this carb with an automatic choke where the choke thermostat is attached to the carb and is heated with hot air from a tube coming from the manifold (heated by exhaust gas)
- 2GE is an automatic choke carb with the choke being heated electrically
What about the carb in the picture from Chile? It’s hard to tell – I would guess it’s a 2GE with a missing choke housing, since there is no choke assembly visible. In fact, in ‘78, at least in US production, GM cars used only 2GC or 2GE carbs.
The arrow in this picture is pointing to the 2GC choke housing.
In a 2GE carb, the only difference is that the housing has an electrical connector and there is no pipe fitting (for hot air) at the front.
Regarding the solenoid in the Omega carburetor above – this is an idle speed control (or idle stop solenoid), usually used to speed up the idle on air conditioned cars or for emission control purposes. It’s not related to the operation of the choke.
In some cases, especially on smaller engines, the idle is set with the idle solenoid energized. When the engine shuts down, the solenoid retracts allowing the throttle to close fully. This prevents run-on when a high idle speed is required.