Question : 3100 seems good then dies

[Saidaigen8]

hi I just finished replacing my head gaskets a few days ago and as far as I know got everything straight except for the serpentine belt. Well I just got a battery yesterday (the cars been sitting for like 6months so old one was long dead) and hooked it up and started it. It ran fine for like 3min. then it would start to sputter then immedieatly die. I tried starting it again then it would go to about 2k rpm and go through the process again of running fine for a few min then dieing. Anybody know where I should start looking?

Its a 94 3100 btw