Hello I have a 2005 chevy colbolt Ss and I blew the motor and bought the same motor for in it then when it came time to fire up it fired right up but after about 10 seconds of it running it starts to idle weird and white smoke pours out the back any ideas on what it could be

 

White smoke out of the exhaust usually means the engine is burning coolant (worn head gasket). Was any work done to inspect the donor engine before installing it?

 

Have you resolved it?