Changing crankshaft bearings with the engine in the car.

Also, consider what some have said. If the bearings and or crank need help, what about the cam bearings? What about the camshaft itself? The lifters? How sloppy is the timing chain? What about the rings? If this is a car you're gonna sell, then shyster it up and unload it. If you plan to keep it, you might want to rethink it.