Started having a problem with my Rochester 2GC on my1962 Buick Special 198c.i. V6. Idles fine, runs strong and pure at 35mph and up. It's that area in between that it stutters, coughs and gasps, then runs great after 35. Just rebuilt with NAPA kit. Idle mixtures set properly. What gives? Checked for vacuum leaks, float level, choke, etc.
Find the diagram in the shop manual (could be about any period GM manual) and look at the path for fuel from bowl to idle passage...if that whole area is dead no matter what, off idle holes or something in the pathway to them has crud in it probably. Some kits contain multiple gaskets to cover different versions, too, and the wrong guess may be blocking a passage. If the thing will run smoothly through the bad area at very slow rate of accel, after you do the above also tour the passages feeding the accel pump and the in and out check valves. If you ever find the EARLY edition of Doug Roe's Rochester book, everyone with any pre Qjet Rochester needs it. The common recent edition dropped 99% of the good stuff on early carbs.
Good info Bruce. Check the adjustment on the accelerator pump linkage too Slim. I've seen a lot of guys who will put a kit in a carb and not check every setting to make sure that they have the settings right. Bruce's gasket theory is good too. I learned the hard way years ago to match the new gaskets to the old gaskets and make sure that they are on right.
Check and make sure the power valve plunger is working and the vacuum passage is clear. Did you install the check ball in the accelerator pump circuit.
And don't this ball just lay in the well at the bottom of the pump cavity? Easy to misplace. Bruce's suggestion on the book is right on. That Rochester bible will heip you dial it in. But first the basics must covered and got right. Matching your new gaskets to the old ones might reveal something.
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