Various bulkhead inserts having a cracked cap are provided. In one example, a cylinder block includes a plurality of cylinder bores, a crankcase disposed below the cylinder block in a vertical direction, and a plurality of inserts, where each adjacent pair of inserts of the plurality of inserts partitions each cylinder bore of the plurality of cylinder bores. Each insert of the plurality of inserts has an upper portion and a cap disposed below the upper portion, the cap cracked from the upper portion and rejoined to the upper portion by one or more fastening devices, the upper having one or more upper bosses, each upper boss having a surface with extruded, circumferentially-extending serrations.