PURPOSE: To unify the supply of cooling water for each engine blocks and improve the cooling efficiency of the engine by a method wherein a cooling water delivering reservoir is formed in the trough part of a V-shaped space between the engine blocks arranged in the V-type and the cooling water is supplied to each blocks through said reservoir.

CONSTITUTION: In the internal-combustion engine, in which two cylinder blocks B1, B2 consisting of cylinder heads 3 and cylinder blocks 4 are arranged in the fore and aft direction of a vehicle so as to form the V-shape, the cooling water delivering reservoirs 19a, 19b communicated with a cooling water pump are formed in the valley of the V-shaped space between each cylinder blocks B1, B2 while both reservoirs 19a, 19b are connected by a distributing pipe 20. Each blocks B1, B2 are formed with water jackets 23 surrounding the upper half parts of cylinders 8a, 8b. Each jackets 23 are formed with inflated parts 24 from the upper parts of the cylinders 8a, 8b to the bottom parts thereof in the direction of said reservoirs 19a, 19b, while the same parts 24 are communicated with the delivering reservoirs 19a, 19b through inlet paths 21, 22.