An all aluminum cylinder block with a Metal Matrix Composite (MMC) cylinder bore was developed which made it possible to re-design the base engine for high performance with a bore-to-bore distance as narrow as 5.5mm. The cylinder block is an open deck type and the MMC preform consists of alumina-silica fibers and mulite particles. A laminar flow die cast process was selected to ensure defect-free MMC bore quality. To insure good lubrication, electrochemical machining was applied to the bore surface.By use of radioisotope(RI) measurements, MMC reinforcement was optimized for wear characteristics. Particular attention was paid to use of fuels with high sulfur levels.