STRUCTURE OF SIAMESE TYPE CYLINDER BLOCK

摘要

PROBLEM TO BE SOLVED: To form a part between cylinder bores of a cylinder block as a common cylinder wall and to shorten the time required for drilling and reduce the occurrence of breakage of a drill when cooling water through-holes to effect intercommunication between cooling water jackets on both sides are drilled in the common cylinder wall by a drill in a state to incline obliquely downward from opening holes positioned on both sides. SOLUTION: Notch parts 10a and 10b are formed in parts adjoining opening holes 5a and 5b of boss parts 8a and 8b for a head bolt positioned outside the opening holes 5a and 5b and an entrance angleθof a drill A with the upper surface 1a of a cylinder block is decreased.