What are the causes of this? The condensation doesn't seem to affect the oil as the buildup is only in the top 1-2 inches of the oil fill tube and a litte on the upper part of the dip stick. The car runs good. It is a fresh rebuild on a 2nd gen ported 6-port. All emissions removed and a fuel computer controlling fuel delivery thru a stock intake.

 

That's nothing to worry about. The top of the oil fill tube is very cold compared to the rest of the engine, and as water leaves the oil (you'll get water in the oil just from sitting overnight and such, doesn't mean a coolant leak) it will condense on the cold upper part of the oil fill tube.

As long as the oil is still oil colored (not coffee or milkshake), and you're not losing coolant, you have nothing to worry about. Mine does much the same thing.

-=Russ=-