Changing crankshaft bearings with the engine in the car.

I would change the oil and try a quality oil
pressure gauge before tearing into it.


Then if required:
I have made a dowel pin kind of a piece and put
into the oil hole and rotated the engine by hand
to aid in getting the main bearings in and out with
the crank in place. Just make sure it is not long enough
to damage the crank.