I have the 1406, which is the electric choke version of the 600cfm. Edelbrock always ships their carbs rich out of the box, so keep that in mind in relation to what your engine size is and can intensity. I had to lower the jet level and the metering springs a notch to get it good on my 260 hp 350ci crate motor.
Mine did the some thing and still would if I start it wrong. Before I turn the key, I push the throttle in about an inch, hold for a second or two, and then release it, just to prime it. It starts perfect after this every time. It is electric choke, so I would close it all the way if it's manual and cold. Firing it up in a rich state won't hurt it unless it's flooded, that's why people want to pump it while they're turning the key. If it's cold, the choke will have to stay closed for quite a while anyway.
Still, if the previous owner modified it a bunch, I would go through it and set everything back to stock and start over. You should be able to get all specs for jets and springs and such out of the carb manual or probably online or something.
Another thing, depending on your intake manifold you're using, you may consider a carb spacer. I went a whole season falling on my face on launches because, I'm guessing there was too much turbulence underneath the carb. And since I put the spacer in, haven't bogged once.
Edelbrocks are not builders carbs, but can be adjusted to work decent if you want to take the time to get to know how they work and play with them. I'm the kind of person who likes to go fast the non-typical way, just because, so I've spent a lot of time with my Edelbrock carb.
Let me know if you have any more questions.