Help tuning an Edelbrock 1406 600cfm

did you set the floats? is the needle valve seating? what is the fuel pump pressure?

If your throttle is fully opening, hold it wide open to clear the flood while you try to start it. Hold the throttle wide open will force the choke partially open if the carb linkage is correct.

Lugnut

I would be checking the float and needle seat first. I would hold the choke plate open and while wearing safety glasses watch down the throat when someone cranks it. If gas is pouring into the carb, then the needle and seat and float need to be looked at. The needles dry out or their slide area gets some 'varnish' in it and makes them stick. Modern fuels crap out the slide area in my carb's float needle every year or so and seems to 'dry out' it's tip every couple years. I have to pull it out for a clean and replace it often.

Mike