Main bearing replacements are dependent on the tolerances when the engine was built. This article explains the main bearing replacement procedure for the 2007-2010 N12 normally aspirated engine along with how to identify the correct replacement bearings based on stampings in the engine block, crankshaft, and the lower crankcase.
For the 2007-2010 N14 turbocharged engine, see Mini Cooper S Main Bearing Identification Instructions N14 engine
For the 2011+ N16 normally aspirated engine, see Mini Cooper Main Bearing Identification Instructions N16 engine
For the 2011+ N18 turbocharged engine, see Mini Cooper S Main Bearing Identification Instructions N18 engine
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