A fuel injector includes a body piece that defines a nozzle supply passage and a chamber in fluid communication therewith and configured to contain a fluid pressure within the fuel injector. The body piece has a threaded segment and a second, unthreaded segment that includes an outer surface of the fuel injector. A tip piece is clamped via a clamping piece to the body piece to form a fluid seal therewith, and a needle check extends within the body piece and the tip piece. The body piece is configured to contain fluid pressures, for example up to and exceeding 200 MPa, and has a wall thickness between the chamber and the unthreaded segment that is linked to a fluid pressure of fuel passing through the chamber. The fuel injector is configured via integrating portions of a nozzle case and a body guide to contain the extremely high fuel pressures.