400 backfire through carb...

[Bandit72]

been working on the charger for alittle bit and got quite abit done, but i still have a backfire through the carb when i go full throttle...it generally does it once, then runs great...it idles alittle rough too...i'm guessing timing, but i wanted to be sure...when it's idling it also smells like it's flooding out pretty bad and if you let it idle for a long period of time, then rev it up it blows black smoke for about 1/2 a second...what do i need to do. I have a new cap, rotor, wires, and the plugs are all clean....maybe a weak coil?

later 

[whitehatspecial]

I would first check to make sure the all wires are installed on the dist. cap correctly and in the correct firing order. Make sure #1 is in the correct position first.

If all that checks out let us know.

[Rolling_Thunder]

total timing is probably way advanced...   

[Chryco Psycho]

a wide open backfire is generally a lean condition , sound like the carb needs to be tuned at idle but maybe not , longer duration cams will smeel rich at idle even if they are set lean due to misfiring cylinders & raw fuel being pushing into the exhaust