In this era where automotive improvement grows fast, cars are more affordable, the need and the interest to own cars increase, metal casting industry is influenced. Casting method using green sand mold generates quality product such as pulley. The testing conducted using quenching results in the chemical composition of casting result which are carbon (C) of 3.1336%, Iron (Fe) of 92.89, Silicon (Si) of 2.0036, Manganese (M) of 0.4795, Copper (Cr) of 0.1729. The cast iron is called mixed cast iron (Si). Micro structure and balding testing were conducted after quenching process and chemical composition testing. Micro structure testing generates Ferit structure whose characteristics are low toughness, high solidity, medium corrosion endurance, and the softest structure among Fe-3C diagram. It is because high silicon content affects the micro structure of grey cast iron. The balding testing using Ogoshi method states that the biggest balding resistant is water quenching with the value of 7.4928x10-7mm2 /kg, and the lowest value of balding resistant testing is the one using SAE 40 lubricant oil with the value of 5.5537 x10-7mm2/kg. The average of water quenching is 6.721 and SAE 40 lubricant oil quenching is 5.805.