FE 390 with 48IDA - need help for setting

[Stephan427SC]

Hi guys,
I have a FE390 stroked to 454cui with 4 48IDA Webers on top. Actually I try to find agood setting of A/F ratio....
Here is what I have : IdleJets : 60 / 70F10, Main jets : F11/75, cam110.
I turned in all idlejets screws and turned them out 1 full turn. Engins runs good and blows a little bit black dust out of pipe while acceleration.....but when I relese the gas pedal the the engine "bangs" out of the pipes ! What do you think is the problem ? Any help and suggestions would be fine - Thanks !

Best,

Stephan

[*13*]

I've attached an example of the weber jetting survey I did a while back. Every engine has different needs so, nothing is set in stone. Two things are pretty certain, when you have your idle circuit sorted out. It'll idle w/o smelling rich & setting the main circuit will be a lot easier. Obviously, the best method for doing all of this is is with an A/F bung on each header pipe. I didn't/don't use this method & it's been a long process.
From what I read, popping out the pipes means too rich. Out of the carbs, too lean.