Blueprinting an engine ,the process of machining an engine to exact factory tolerances or closer , such as making all clearances to each component the same for instance all rod and bearing clearances equal, piston to wall clearances, equal deck height , combustion chambers etc. to exacting clearances per the blueprint or closer , factory production tolerances are suppose to be close enough for average every day use/ service life. fitting each part to a given spec. or closer with less variation .