An engine block of a diesel engine cast integrally with the cylinder head, with a number of cylinders in line, including an outer wall (21) and a cylinder wall (13) for each cylinder with a first cooling space (22) for a liquid cooling medium and with a second cooling space (25) on top of a cylinder ceiling (14) with openings (15,16) for gas exchange valves, the first cooling space (22) enclosing all the cylinder walls (13) entirely. In order to strengthen and cooling the vulnerable zone at the transition from cylinder wall (13) to cylinder ceiling (14) the first cooling space of adjacent cylinders forms a gap (23) with a width (35) constant or increasing from top to bottom.