[Steeveedee]

If you have the initial timing correct, the first thing I would suspect is that the carb is jetted too lean. I had a 1406 on my 305 CI in my Skylark, and with headers you will have to feed it a little more fuel. I think that I went 4 numbers richer on the jets but don't remember what I did with the metering rods. You will need to buy the kit. It isn't that expensive, and should give you what you need.

Mine would stumble off idle, but if I went heavier into the throttle, the accelerator pump would cover the lean condition just enough to start laying rubber. Does yours cover the stumble if you stab the throttle harder? Or does it just backfire?