my blazer lt 98 ,piston and piston ring was changed,air filter was checked ,exhaust still smoke,help me ,please????????

 

What color smoke? when does it smoke... we need more details.

 

smoke color is blue-grey,,, first time starting engine after the piston,piston ring,valve seal,changed. mechanic have checked air filter,cylinder head and he said ok,try to start engine,,but the exhaust still smoke ,,,,help me please??.