So after finishing the full rebuild on my 3100 1994 buick century .... new gaskets, pistons, rings, pumps ...

The first thing I noticed there were water droplets on the oil cap, and after running it a bit more, brown slugde on the radiator, so the water has oil...

I dont see milky stuff on the oil cap yet just clear water drops.

There were times when there was smoke under acceleration only, i cant remember the color, but now there is just a little but barely noticeable, i havent taken it for a ride again.

There are no air bubbles accelerating in the radiator fill tube.

Can you help me with this, no idea where to start.. it was a very hard job to do finding all the pieces to rebuild, and then have these issues after so much effort...

Do a running compression test.

. . . and:

How was the block cleaned inside and out?

Was all of this done indoors?

Are you in a humid area?

I was in the garage, We cleaned it with gasoline.. it dried quickly but but yes, there was rain those days, I guess it was that because, the drops on the oil cap stopped showing...

I will flush the radiator and try and check if there still oil in the system.

Ah okay I don't know what residue plus gasoline plus coolant will turn into. Maybe that'* part of the issue. Or maybe the brown sludge is some old Bar'* Leaks working its way through.