[Pete Munroe]

In my distant past there was a Rochester 2-bbl on a 389" Pontiac...pretty much the same basic design...when the accelerator pump starts to leak the pump shot is too weak...a very easy rebuild as I remember it, the accelerator pump is a vertical plunger, if it has worn out, put in a new one and squirt the rest of the carb clean with cleaner a few times with an aerosol can of Gum-Out or whatever carb cleaner...try not to get it sprayed in your eyes...

Just be careful, get a toothbrush..clean the dirt off the outside of the carb before you take it apart...keep things clean...paper towels, clean dishes and pie tins for screws, etc...if you don't have compressed air use the carb cleaner can to back flush jet passages...

Could be timing, check all that stuff first...inside the distributor cap for deposits, the rotor for wear, bad gaskets on the carb base...but most likely it will be a worn out or damaged accelerator pump.

Pete

If the timing has changed a lot, you may have a bad distributor gear, cam gear or chain... not likely, but it could happen...

Pete