Heater core swap.

I just changed the heater core in my 93 grand am and am haveing a hell of a time getting the water to circulate back through the system. I let the car run till thermostat opens and temp climbs real fast to hot. I shut it off let it cool and try again. I have repeted this 4 times and still no good. I even tried swapping the lines in case it was a one direction flow. What else can I do?

Are you sure the thermostat is opening? Are the lines hot on both sides of it, and on both sides of the radiator?
Things to consider, check:
-Air in system, try loosening hoses, squeeze the lines until coolant runs out.
-Bad Thermostat
-Restriction
-Broken water pump vane.

Good Luck

As Dragula says, most likely an air lock.

Look for the highest point in the cooling system, there should be an air purge screw, open it until a steady stream of coolant comes out.