off idle stumble

[jdl71]

If this is better suited somewhere else, please mods feel free to move it.

I have a '64 230 with a rochester B. I currently have a rebuilt carb on it that I purchased from a member here. It has a new fuel pump, clean gas tank, filter and lines. I have tried running it from a gas can with an electric pump, made no difference. I found a fairly major intake leak near the rear of the gasket. New felpro intake and exhaust gaskets, no change. I have adjusted the timing both directions, ensured the advance is working and tried the fuel/air mixture screw. I have new plugs, wires, cap, rotor condensor. I do not think I've done anything with the points. All have been done since I noticed this problem, with the exception of the plugs. I do not remember for sure if it was doing this before I changed plugs. The truck had been sitting for a long time before I got it. I do remember having a hard time finding plugs because it still had the original AC plugs in it that are a discontinued part number and the part number that is listed for my application is a longer plug. I did gap them, and as I recall they were the same heat range. Could this be the issue? It seems to me like a lean stumble as adding choke helps, but doesn't make it completely go away, and if I hammer it too hard off idle it will backfire up through the carb. Any and all help is appreciated.

http://www.youtube.com/watch?v=tuHGQkASnc4