I asked you to check the plugs and the RPM that it cleans up, because you very easily could have fouled plugs from the poorly tuned first carburetor. You could also very well have a vacuum leak on the intake. Also the total timing is actually more important than initial timing.
Unless an Edelbrock operates differently than a Holley on the idle circuit, you should be able to screw in the two mixture screws the complete way, and kill the engine. If the engine continues to run with those screws bottomed out, the carb has a fuel leak somewhere or is running on the secondary being out of adjustment.
I'm not sure how experienced you are in initial carb tuning, checking timing, and sealing an intake. But the Blackness of the plugs and the fact that total mechanical timing has not been checked, is really putting the cart before the horse.
First thing I would do is buy a new set of plugs. Check mechanical total timing. And check for vacuum leaks.
You may want to give Tech a call on Monday or we can have a call on Monday.
A super rich mixture gets gas into the fuel, thins the oil, and can be a big problem.
