hard starting....

[GMC Guy]

so i'm having a problem with my truck starting back up again after about 30 minutes or longer. i have a brand new edelbrock 600 cfm carb that runs great and starts no problem in the morning when everything is completely cold. so i know the electric choke works ok. but if i drive the truck somewhere and leave it for a little while it doesn't like to start up very easy at all. it'll just crank and crank until finally i have to pump the gas enough to get it to finally start (which it barely does). my old quadrajet would start no problem after hours of sitting...as long as i held the gas pedal down about half way. i tried this method with the edelbrock and doesn't seem to work. is there anything else that could be causing it to be so stubborn? or maybe my starting technique is all wrong...
any advice is appreciated. it's kinda embarrassing sitting in a parking lot and having everyone stare at you while your truck just keeps cranking and not starting...