ABSTRACT: A gray cast iron cylinder block is the standard design for automotive applications. For diesel engine application, separate dry or wet liners which made from special wear-resistant materials are used to perform more reliable and durable product. While the cylinder blocks for truck engines continue to be manufactured in cast iron, aluminum passenger car blocks are becoming increasingly popular owing to their weight saving potential This chapter is to study the process of the designing and development of gray cast iron cylinder block casting. The aims of this product is to reduce the product weight, increase the cold start conditions for emissions, improve the design passages of the oil breather system and trim down the rejection rate by improving the process quality. Due to the limited investment, the design of the casting product are being limited by engineering aspects such as jigs, fixtures and other related production processes.