The reason engines smoke when the valve seals are bad, especially on startup, is that the oil in the head leaks past them into the cylinders when the engine is off. it then tens to lessen or go away as you drive. Smoking all the time usually means the rings are bad and oil gets past them because of crankcase is pressure.

Oh BTW I have 2 complete sets of valve stem seals from my Engine Gasket Kits from the dealer... how much are they worth?