When I want to check for rod bearing wear, I run the engine to make sure that there is an oil film on the rod bearings. I set the particular cylinder at TDC and put a dial indicator end on the top of the piston through the plug hole. I then wiggle the crank + and - 10 degrees. A good rod bearing will show an even sweep of the indicator. A bad rod bearing will show a flat spot in travel. It will show a bad rod bearing before it makes noise. It is a very sensitive and accurate test.

Matt De Maria
Owner/Technician
Stuttgart Performance Engineering
Gaithersburg, Maryland, USA