Torsteinsen Emigration

My great great grandfather, Torstein Torbjørnsen, emigrated to America in 1880. I have found his family in the 1865 and 1875 Census living in Fjelberg, his father's name was Torbjørn Torsteinsen and his mother was Anna Iversdatter. In the 1875 Census Torstein had two sisters Siri, b. 1860, and Britha, b. 1863, and two brothers Johannes, b. 1866, and Torbjørn, b. 1870. A brother Iver, b. 1857, per the 1865 Census presumably died as he is not in the 1875 Census. Torstein came to Wright County, Iowa and took the name Thomas T. Hill. I have located Torstein's brother Torbjørn, also in Wright County, Iowa, in the 1910 Census. He took the name Ben T. Hill. But have not been able to find Ben (or Torbjørn) on the passenger lists, or to determine when he came to America. Can anyone help me find when Ben came to America. Also, I don't know if any other members of his family emigrated. Any help would be greatly appreciated.