because one of the valves arnt closing or opening properly
The smoke you see may be moisture/steam. The heater core is probably leaking engine coolant. If the "smoke" has a sweet smell to it, it's engine coolant. More info about the vehicle such as model and year would help.
because the fan belt is burning
fabreeze!!
You probably have a coolant leak. http://www.autozone.com/servlet/UiBroker?UseCase=S001&UserAction=viewSimpleDiagInfo&Parameters=info answer The coolant is most likely leaking onto the engine of your car, causing the white smoke.
The carburetor needs calibration or changing of possibly defective part, for example, gasket or needles.
The engine seems to have some problems why it releases smoke. It would be much better if you will check and repair it to a mechanic immediately.
febreeze spray
Find and fix exhaust leak
Sorry to tell you but you have a blown head gasket, cracked head, or both. The white smoke is coolant entering the combustion chamber. STOP driving this vehicle or you will destroy the engine. You must have this repaired and it is not cheap.
The smell will give it right away.
look for a leaky fuel line
White smoke coming from the engine can mean many different things. One such thing is that your car may have a blown head gasket or that oil is burning in the engine.