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View Full Version : Rochester 2 barrel carb



jsipe007
November 29th, 2013, 08:00 PM
Hey guys I'm looking for a Rochester 2 barrel carb for my dad and my 46 cj2a. Preferably a Rochester 2g or GC but basically just in need of a reliable 2 barrel carb to get her on the road. The current carb we have is dumping fuel through the venturi, we think the power valve and piston may be the issue, mainly the power piston. We've rebuilt the carb twice and tried just about anything we can think of. Looking for suggestions/options!
Thanks!

69cj5
November 30th, 2013, 07:55 AM
Sounds like either the float level is wrong or the needle valve is not seating.

jsipe007
November 30th, 2013, 09:04 AM
Thanks for the input! We will check both to be sure.

Let me see if I can detail the problems bit better. Its a 2g carb on a 225 Buick v6

Under large acceleration, the acceleration pump kicks in and the jeep sounds good and doesn't appear to be running rich. At idle, fuel is properly vaporized and the jeep runs pretty good. Under light acceleration, fuel drips from the venturi, causing the engine to run really rich and become slightly flooded at slight accel, stumbling and running very right.

If I understand the carb right, the power piston and power valve utilize engine vacuum changes to provide fuel to the engine under light accel but it is very possible there is an underlying issue. We tore down the carb again last night and all small passages are clear. Thoughts?

Also, does it matter which gaskets are used? I've watched a couple 2g rebuild videos and we believe we are using the proper gaskets for the bowl and after the butterfly

69cj5
November 30th, 2013, 09:22 AM
Not sure about that exact carb, but unless you are standing under the hood driving down the road, or you installed an o2 sensor and watching it on a computer of some sort as you drive, I don't see how you can tell if it is rich off idle

Typically a stumbling off idle is a too lean mixture as the vacuum is dropped when the throttle blades are opened. This happens with most carbs, that is why there is a accelerator pump. That pump forces additional fuel in as the blades open during the period of low vacuum reducing stumbling.

Generally a stumbling is fixed by adjusting the accelerator pump linkage to force it to come on quicker. This should be a simple adjustment. If you are starting to bend linkages, stop.

You said you rebuilt it, that kit should have come with a new accelerator pump diaphragm. Did you install the diaphram correctly? If you did not use a kit to rebuild it, go get a kit and rebuild it. It is cheap and pretty easy.

Don't bother getting another carb because then you just have to tune that one.

If all fails I have a brand new never run Holley 4 barrel that I will sell you. It has to be tune too, but it is new and is the one for that engine. It is a 4 barrel though, so you need a different intake to run this one.

jsipe007
November 30th, 2013, 01:21 PM
Great info thanks! Its very likely the engine is running rich, just easier to tell when under light power. Linkages and everything look fine, accelerator pump seems to be working as well. We've used teo separate carb rebuild kits. The piston and power valve are re used though and not in the kit

69cj5
December 1st, 2013, 07:21 AM
It could be both. You may have the jetting a bit fat, and the accelerator pump needs to come on a bit earlier as well.