An internal combustion engine having a cylinder block made of a light-alloy with a cylinder wall around a cylinder bore including a cylindrical fiber-reinforced portion which is formed of a mixture of an alumina-based fiber and a carbon fiber with a light-alloy matrix. The alumina-based fiber has a fiber volume fraction set in a range of 8 to 20%, and the carbon fiber has a fiber volume fraction set in a range of 0.3 to 15%. The alumina-based fiber contains 25% or less, by weight, of silica, has an average aspect ratio of 20 to 150, and an alpha rate of 2 to 60%. The carbon fiber has an average aspect ratio set in a range of 10 to 100 and a Young's modulus set in a range of 20 to 30 t/mm.sup.2. The piston for the cylinder bore has an iron-plated layer covered by a tin-plated layer. The piston rings for the piston may be of austenitic stainless steel to provide thermal expansion characterics similar to the cylinder wall and may be provided with a nitride or chromium-plated layer.