Multi cylinder internal combustion engine comprising a cylinder head internally defining exhaust passages

Abstract

In a multi cylinder internal combustion engine comprising a cylinder head internally defining exhaust passages and a converging area into which the exhaust passages converge, an upper water jacket and a lower water jacket are formed above and below the exhaust passages, and the lower water jacket has a greater volume than the upper water jacket. Thus, the cooling efficiency for the converging area can be improved by increasing the volume of the part of the water jacket adjacent to the converging area. Also, because the upper water jacket has a relatively small volume, the load on the core parts supporting the core part for defining the upper water jacket can be reduced, and the overall mechanical strength of the core can be improved. By extending the water jackets to the converging area, the cooling efficiency can be improved even further.