Abstract: There is provided a water jacket spacer set in a groove-like coolant passage of a cylinder block of an internal combustion engine including cylinder bores and set in an entire circumferential direction or a part in a circumferential direction of the groove-like coolant passage when viewed in the circumferential direction, wherein a coolant passage opening through which coolant flowing on the rear surface side of the water jacket spacer passes to flow to an inner side of the water jacket spacer is formed on at least one place of upper portions of inter-bore portions, a guide wall for guiding the coolant is formed in a vicinity of the coolant passage opening, such that the coolant flows into the coolant passage opening; and an inclined wall is formed on the rear surface side of bore portions of a position where the coolant is supplied into the groove-like coolant passage, the inclined wall extending with an upward inclination to create a flow of the coolant toward the coolant passage opening.

Abstract: There is provided a water jacket spacer set in a groove-like coolant passage of a cylinder block of an internal combustion engine including cylinder bores and set in an entire circumferential direction or a part in a circumferential direction of the groove-like coolant passage when viewed in the circumferential direction, wherein a coolant passage opening through which coolant flowing on the rear surface side of the water jacket spacer passes to flow to an inner side of the water jacket spacer is formed on at least one place of upper portions of inter-bore portions, a guide wall for guiding the coolant is formed in a vicinity of the coolant passage opening, such that the coolant flows into the coolant passage opening; and an inclined wall is formed on the rear surface side of bore portions of a position where the coolant is supplied into the groove-like coolant passage, the inclined wall extending with an upward inclination to create a flow of the coolant toward the coolant passage opening.