Engine pop sound problems help

I have an 82, my problem is that when mi thank goes below 1/4 i have problems when taking off, if i hit the gas pedal hard my it will die, after a while driving arroun 70-80 mph i don have problems with that, im assuming it has to do with problems with not warming the engine properly but i warm the engine at least 15 min, i took it to my mechanic he said it could be a problem with the carburator, this start to happen after a few times my gas thank droped below 1/4, when its winter i have to warm the engine for a long time or it will die, also some times it will go crazy on the rpms, please help im new into engines and that tipe of stuff.