New bearings, difficult to rotate the crankshaft.

Remove your rod caps one at a time and turn the engine over each time you take one loose.That will help you determine which one is the problem(if it is only one). When re-assembling a motor you should rotate the assembly each time you put a bearing in and then if its tight you will know which one is tight.Oil on the back of your bearings will not cause your engine to turn over hard. The oil will squeeze out as you tighten it down. You have something solid binding up. Is the engine in the car and does it have spark plugs in it? that will also make it harder to turn(but not That hard)