Abstract: An internal combustion engine includes an engine block having a head seat surface and a cylinder opening extending from the head seat surface into an interior of the engine block, and a cylinder insert residing within the cylinder opening and having an insert upper surface substantially flush with the head seat surface of the engine block. The cylinder insert has a smooth cylindrical inner surface with a longitudinally extending cylindrical axis, and a stepped outer surface formed of three longitudinal regions. The three longitudinal regions include a first longitudinal region adjacent to the insert upper surface and having a first wall thickness, a second longitudinal region remote from the first longitudinal region and having a second wall thickness less than the first wall thickness, and a third longitudinal region intermediate between and continuous with the first longitudinal region and the second longitudinal region.