When a cylinder block is cast, a bearing housing is constituted by a preform integrally cast with the cylinder block. In order to raise the strength of the bearing housing, a metal matrix composite is formed around the preform. The preform is constituted by a high volume factor member having a relatively high volume factor and two low volume factor members having a relatively low volume factor connected with top and under surfaces of the high volume factor member respectively. The high volume factor member is made of solid metal and the low volume factor member is made of sintered metal filaments. Base material of the cylinder block infiltrates into the low volume factor member to form a metal matrix composite in the preform.