"because when it got rebuilt for some reason it got extremely dirty in the system and theres a crapload of what i think was old rust and alot of machine oil to keep the head from rusting (the inside of it wasnt painted)."
....maybe a mouse built a nest in the engine before you picked it up???? Was all the holes plugged? maybe not the radiator's fault?? Just curious. Makes sense, as you mentioned, to flush the entire system.
