Closed deck type cylinder block and method for producing the same

摘要

A closed deck type cylinder block providing an optimum area ratio of opening at a top deck side, and a method for producing such cylinder block having the reduced area ratio of the opening at a reduced energy cost and with reduced labor, yet exhibiting smooth discharge of waste sand converted from a water jacket core through the opening in spite of the reduced area ratio of the opening. The cylinder block (10) is formed with a plurality of cylinders (10d) juxtaposedly arranged to each other and a water jacket portion (10a) surrounding the cylinders (10d). An upper end of the water jacket portion is open at a top deck and is partly covered with bridge portions (10c). The opening (10b) has an area ratio of from 10 to 30% of a projection area (10a) of the water jacket portion at the top deck surface.