ok i just got the car running and back together after putting a new head on and gaskets

car starts up fine and runs great, butt when i pulled the oil cap, i feel air comin out of it and it smells like exhaust(almost)

did i do somthing wrong here.
also on my way home the temp sky rocket to the top so i pulled over and check under ther hood and didnt see any water at all, when i got back in the car to turn to key to see where it was it was at 1/4 way up, in less then 2 mins??? got the car home since i was just around the block and i hear a hissing noise comin from the rad cap so i replaced it with another one i had layin around, filled it up again and bleed the system again. could that have been the cuase of my temp getting hot?