The car runs great, even better now that it has a new O2 sensor. Has a rough idle, and the occasional fits of smoke, but other than that it runs like new. I have no idea how long the engine sat. My mom owned the car when the last engine was hydrolocked. Whiteside chevrolet in ohio found this engine, only had 22,000 miles on it, and put it in. My mom said it always smoked every now and then when you start it up, but never like it did yesterday.

Sounds like a bit of condesation after you warmed it up and let cool down, the bit o smoke was normal.
If you suspect a bad valve or seal do a leak down test after you take a compression test, both of which I think you would pass.

I dunno... I wouldn't expect to see condensation unless the ambient temperature was down around 40°-50°F outside at most.

I'm wondering if you might have a very slow coolant leak into one cylinder, and thus you're seeing white coolant smoke rather than oil smoke (which I would expect to be noticeably blue, not white).

Alternatively, if it definitely is oil smoke, but doesn't occur very often, maybe it'* a valve seal that leaks down only if the engine is stopped with the offending valve in the open position.

Th e way that smoke comes out of an engine is very tell-tale. Smoke at start up (white) is either condensation within the engine or exhaust or a slight coolant leak after shut down. Have you lost any coolant within the overflow or is is stained or dirty within the tank? Generally an oil leak is blue and comes out on acceleration (rings) or deceleration (valve stem seals)(because of extreme vacuum within intake). For the time and money that it takes...a compression test tells alot!!!

I know what burnt oil smells like, and this has a burnt oil smell. My car hasn't lost any coolent since I did the change a few weeks ago. Its not condensation cause when it has these fits the car has been running for a while. The last fit of smoke was in Gettysburg last weekend sitting idle in a Gas station parking lot after the car has been run for over an hour. Its not a constant thing. Seems to smoke for about 1 or 2 minutes after the car has been run a while. Its not often. I'd say once every 2 weeks, and getting less and less.