Engine bearings are designed to last for a long time when they are properly installed and supplied with clean oil. When a bearing fails early, the wear pattern on the bearing usually points to the root cause. Identifying that cause is essential, or the new bearings may fail the same way.
1. Contamination
Dirt, machining debris, and metal particles are among the most common causes of bearing damage. Particles can embed in the bearing surface or score the crankshaft journal. Prevention starts with thoroughly cleaning the block, crankshaft, and oil passages after machining, and keeping parts covered during assembly.
2. Oil Starvation
Without a continuous oil supply, the oil film breaks down and metal-to-metal contact occurs. Causes include low oil level, a clogged or poorly sealed oil pickup, a worn oil pump, restricted oil passages, and running the engine dry on its first start. Prime the lubrication system before starting a freshly rebuilt engine.
3. Incorrect Oil Clearance
Clearance that is too tight can prevent an adequate oil film, while clearance that is too loose can reduce oil pressure. Measure journals and verify clearance during assembly rather than assuming the parts are correct.
4. Assembly Errors
- Bearing caps installed in the wrong position or direction
- Dirt or oil trapped behind the bearing shell
- Locating tabs not seated in their notches
- Incorrect bearing size for the journal
5. Journal Condition
Journals that are tapered, out-of-round, or rough concentrate load on part of the bearing. Inspect and measure every journal, and have the crankshaft machined when it is out of specification.
6. Excessive Load
Detonation, lugging the engine at low speed under heavy load, and overheating can all overload bearings and break down the oil film.
Evergreen Bearings
Evergreen main and rod bearings are identified by application and size. Use the Evergreen eCatalog to find the correct bearings, and refer to our article on bearing sizes before ordering.
