You have checked the crankshaft and found the rod journal surfaces are smooth. What should you do next?

When the rod journal surfaces of the crankshaft are smooth, the next appropriate step is to install standard bearings in all rods. The condition of the journal surfaces is crucial because smooth surfaces indicate that they have not experienced significant wear or damage, which is necessary for proper bearing performance.

Standard bearings are designed to fit snugly on properly sized and undamaged journal surfaces, ensuring optimal lubrication and minimal friction during operation. If the journals are in good shape—with no excessive wear, scoring, or out-of-round conditions—there's no need to adjust the bearing size or modify the crankshaft. Using standard bearings promotes reliability in engine operation.

The other options involve using undersized bearings or grinding the crankshaft. These steps are typically reserved for instances where the journal surfaces show wear, damage, or are out of specification, which is not the case here. Therefore, standard bearings are appropriate for maintaining the functionality and performance of the engine in this scenario.