Abstract: An improved arrangement of a hydraulically-actuated injector fuel system is disclosed for an engine having an engine member such as a cylinder head. The system comprises a hydraulically-actuated injector positioned in a injector bore defined in the cylinder head and apparatus for supplying hydraulically actuating fluid to each injector. A hydraulically-actuated injector fuel system requires apparatus for communicating fuel and actuating fluid to each injector. An engine equipped with externally disposed actuating fluid and fuel lines exhibits a complicated and costly construction which is difficult to service. The present invention provides separate actuating fluid and fuel manifolds or passages which are internally disposed in the engine. This hidden and integrated arrangement is not only esthetically pleasing but simplifies assembly and disassembly of the engine and also permits a reduction in cost of the engine.