Hi everyone. Just looking for some ideas and opinions. I have a 1971 C3 that I bought in Nevada exactly one year ago. Since I’ve had it always had an issue with the Holley 350 cfm carb that was on there.  The car has been sitting a lot prior to me purchasing so I figured the carb was all bunked up. I had a mechanic take it apart and clean it until I could purchase a new one. I’ve given it new plugs and wires, new battery, new starter. It was running good until I ran out of gas at my house because I would start it and let it run every other day. Since running out of gas I have not been able to start it. I put in 10 gallons. I have now put a new carb on thinking maybe if there was something in bottom of tank it clogged up carb...  well I’m getting gas, I’m getting spark, and since I put in new carb it sounds like it wants to turn over so bad.  It hiccups (and some smoke will come out of carb) instead of just turning over. I’m now thinking maybe distributor may be outta whack ..  IDK.  Again it cranks, but will not turn over.  Ty everyone for taking time to read this 

A few questions.

First of all, a Holley 350 cfm?  That makes no sense. 

What is the new carb?

Did it run when you bought it in Vegas?

Are you going to work on your car or pay somebody to do it?

Have you moved the distributor?

Hopefully others will chime in other than the 6ish regulars. 

Most obvious answer would be the problem is in the NEW carb, since you state it would start and run before.

What kind of carb did you install?

Does it fit the intake manifold correctly, and have the proper base gasket to seal to the intake?

Are all of the vacuum hoses connected properly?

I assumed you meant 750 cfm and then thought you had a LT-1.  I'm guessing like the others said that something is wrong w/ the new carb or installation (most likely).  Was the new carb adjusted properly?