Improving the quality of metal castings for serial production of automotive industry, leading to improvements in the properties of casts and their lower costs. This publication analyzes the non-metallic inclusions contained in casts of heads of internal combustion engines, molded of Nemak Czech Republic, Ltd. Tackling includes analysis of size, shape, chemical composition and hardness of the specific non-metallic inclusions. The thesis describes the purity metal holding furnaces and proposals to eliminate inclusions from metal.