The hardness of the cylinder block is studied using Brinell-Hardness testing machine. Tooling problem occurred castings were collected for analysis. From which hardness testing carried by Brinell hardness testing machine and the hardness values observed with higher side against the specification. Followed by micro structure evaluation comparing with the ASTM A 247 standard. And the graphite form present Type D and E instead Type A graphite. Knowing the constituents present in it, properties of every single metal present in it, is studied and modifying the alloying elements; Copper (Cu) & Tin (Sn), as Pearlite structure and hardness greatly depends on it, the hardness of the cylinder block is improved. Hence, this could be easily distinguished by being compared as, before and after. The Before criteria, states a failure sample with a higher Cu and Sn composition along with the alloy composition, whereas, the After criteria, states an optimised sample with reduction of Cu and Sn composition along with the alloy composition of the analysed diesel engine block .