Rochester 2G Help

After a second rebuild by The Carburetor Factory on my Rochester 2G, I continue to have run on and noxious fumes. I have adjusted the set screws and idle every which way and replaced the choke cable. Replaced teh fuel filter. It sometimes runs smoothly but there is a flat spot on immediate gas pedal depression at times and in general it seems like it should work better. I put about 1000 miles a year on it. 1967 original 225 V6. 76,000 miles and never rebuilt. It used to not be this way and is it just my engine finally needing more internal attention or do I need to replace the carb with a different Rochester 2G? Does anyone make a new replacement for these?
Thank you.
Peter

 

What does The Carburetor Factory say? Has a rebuild been recent enough that they can comment to your questions?

 

A couple of easy tests - first, make sure that you can kill the engine by screwing the idle mixture screws all the way in. If not, you are not running on the idle circuit at idle and something else is goofy. Second, the engine should also die when you close the carb flap completly; ie back off on the curb idle screw until the engine dies or there is a gap between the screw and the linkage. If there is a gap and it won't die, check for vacuum leaks - a leak bypasses the throttle plate so the engine won't die. Check for vacuum leaks.

With the engine at operating temperature, the choke is completely out of the picture - flap wide open, fast idle cam clear of the linkage.

Choke, idle mixture, fast idle stop, idle stop, pump shot are about all you can adjust externally on most production carburetors. Problems most often come from vacuum leaks.

 

Thank you. Yes the engine dies when the screws are all the way in. I have not checked for vacuum leaks so that could be an issue. The Carb Factory likes the carb out of the jeep to work on. So I have not gone back to them. It was rebuilt last year. About 1000 miles ago.
Thank you again and vacuum leak is my next check.
Peter

 

One area in particular to check for vacuum leaks is at the back side of the carburetor base gasket.

The carburetor has a passage that exhaust gases pass through/under and these exhaust gases can deteriorate the base gasket.

These passages can be plugged off if desired, they are there for quicker warm ups in colder weather.

 

When you sent your carb to be rebuilt, did they rebuild your original carb or replace it with one of their already rebuilt units. What is your carb GM number? Rochester 2G came in several different models and sizes to fit even chevy truck v8's. Yes they look the same and will bolt directly on but have a bit larger bores.

 

Timing chain worn?

 

I can verify what Walt said, I took a Rochester 2gc off a Dauntless in a Commando and installed it on a 350 SBC in my 72 C50 Chevy. Runs fine! However not knowing the lineage of the carburetor, it may well have come from a similar truck. After owning 4 CJ 5's, 2 CJ 6's, 3 CJ 7's and 1 CJ8 not much surprises me!

 

The Carburetor Factory rebuilt my original factory one. Not sure of the GM numbers on it. I checked the best I could on vacuum leaks and nothing is obvious. The gasket was new when it was rebuilt. I am about to take it to an shop to get a second opinion since I have had no luck. The guy has a good track record with old jeeps.

 

I'm in the middle of a carb rebuild and have determined that the 2g (along with most old carbs) take issue with re-formulated fuel. Rich running needs to looked at for mechanical issues as well as carb settings.
If it's determined mechanical issues and tune (especially dwell/timing) are not causing rich and run on (dieseling) the carb may be the source. Today's fuel needs to be run leaner (in today's cars, yet riched in older vehicles designed to run on leaded fuel). This is not always just re-jetting as several circuits internal to the carb can provide too much fuel.
I typically will give a little more initial timing that is spec'd (for back in the day fuel) and sometimes open up the spark gap just a touch, especially if running electronic ignition.
There is too much internal to a carb to address circuits and mods to richen air/fuel mix.
Best compromise is to keep the engine in good tune with a little more initial timing and perhaps richen it a little by sourcing and installing larger jets. Sometimes it's trial and error to find the right jetting for fuel and elevation you live.
I had to edit this as reading last nights post I had a couple spelling and word errors.