| 摘要 |
PROBLEM TO BE SOLVED: To prevent the generation of knocking and suppress the distortion of an exhaust valve seat by directly guiding the cooling water from a water pump not only to a cylinder block side but also to a cylinder head side to avoid the temperature rise in the vicinity of the valve seat. SOLUTION: A first cooling water passage 46 is formed along cylinder bank direction on the outer wall surface of the cylinder block 4 so as to be connected to the discharge side of the water pump and located on the outer wall side from a cylinder block-side water jacket 38. The cooling water passage 46 is provided so as to be connected to the cylinder head-side water jacket 40. A second cooling water passage 48 allowing the middle part of the first cooling water passage 46 to communicate with the cylinder block-side water jacket 38 every cylinder is formed.
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