Engine knock when car is cold, goes away when warm.?

this could be a timing knock but I doubt it a engine knock would not normally be from the top end, cold lifter noise maybe, but no deep bearing knock, have you had a real mechanic even check? what did your mechanic say? there is no preventative way to change too much oil, taking some out usually solves the problem. Usually if too much oil was in an engine the front or rear seals my leak ,after many thousands of miles, but not knowing the make or model of car, because you did not say, we cannot even speculate about the cars with top end noises that we are aware of, because you failed to mention the vehicle anyway. good luck hope it works out.