How Do I Know What Size Crank Set Bearings to Get?by Robert Bayly
A crankshaft bearing set consists of the main and rod journal bearings. The main bearings support the crankshaft in the engine block and the rod bearings support the connecting rods on the crankshaft. These bearings generally come in four sizes: standard, .010 oversize, .020 oversize and .030 oversize. Oversize bearings are used when a worn crankshaft is resized. The resizing process removes material from the crankshaft and thicker bearings are needed to compensate.
Remove at least one bearing half from a main bearing cap and a connecting rod cap. Clean the back of the bearing with parts cleaner and a shop rag.
Look at the back of the bearing for the size that is stamped into the edge of the bearing. If you are only replacing the bearings, you will want the same size that is stamped into the back of the bearing. It may be std., .010, .020, or .030.
Take the crankshaft to a machine shop for machining. Depending on the condition of the crankshaft, you may need different bearings for the mains and rods. For instance, the crankshaft may need .020 oversize bearings and the rods only .010. If the crankshaft is machined, the machinist will tell you what size bearings you need.