71 383 w/AVS. Engine stumbles initially, but if I keep the throttle open, it picks up again & pulls pretty hard. I've tried adjusting the accelerator pump in each direction & neither position stopped the stumble.

I'm starting to lean toward an ignition problem. The plugs were really fouled from a previously corrected problem, so I cleaned 'em up with carb cleaner & a wire brush. My timing light also seems to have a problem triggering off the ignition wires (the light works just fine on my factory wired Dodge Ram). I guess I'm just not sure it's a weak spark since I wouldn't expect it to pull hard after a couple of seconds of sumbling.

Any ideas?

I had a consistent off idle stumble with my 360 and 650AVS. I tried everything and finally read somewhere that the Eddy carbs don't like more than 5 psi of fuel pressure. I added a fuel pressure regulator, set it at 4.5 psi, and no more stumble....at all! It also idles cleaner.

Never woulda thought of that one on my own. There's a Jeg's nearby; I'll see if they've got a regulator. It's using a stock mechanical fuel pump, but still wouldn't be a bad idea to see what kind of fuel pressure it's pushing. BTW, nice Challenger!

In my AVS i have to replace the accelerater pump 'piston' quite often or i get off idle stumble. The leather ring will loose its seal in the bore and not pump the proper amount of fuel. Just a thought...

Look at the check valve in the accelerator pump well. If it is not holding you will get a weak pump shot.