Nissan Repair: 1998 nissan sentra engine smoking, valve stem seals, nissan sentra

Question
Von once again I need your help. In October 2007 I took the engine out of my 1998 Nissan sentra to comfortably change a few parts. I had the engine sitting until July this year when I put it back in. After a few days of driving the vehicle it began smoking(white color). I check the spark plugs and the were black with oil on the threads. The engine ran Fine with no miss. I change the plugs with the same smoking problems. I asked a few buddies and the convinced it was the valve stem seals and I put the head in the machine shop to replace the seals and get reconditioned. Just after viewing the head after getting it from the shop I had a feeling it was not done properly because it was dirty. I place the head back on the engine started it up and it began with the white smoke after it reach the heated temperature. There is no coolant in the oil nor is there any engine miss. I also changed the pcv valve. Please tell me the problem the smoke is not blue and the smoke is not heavy white it look like a heavy mist on a cold morning but it is smoke and you could smell it. help help. I would like to fix the problem without replacing the engine.

Answer
Kingsley,

If the smoke smells like oil the rings may be sticking.  An engine flush might get the rings unstuck.  Basically, add a quart of the engine cleaner and follow the directions on the can for how long to run the engine before you change the oil.  If the smoke does not smell like oil it is water and you probably have a cracked head that will require welding or replacment.  Nissan blocks are pretty much soild and I have never seen one that has cracked.  So, if it is white smoke and not in the oil but white smoke out the pipe then you are looking at water entering the exhaust and coming out the tail pipe.  Have the head checked for cracks and let me know how it goes.