After his first Indy 500 Horn felt that he failed to make an impression. Former driver turned car owner Harry Hartz felt otherwise about the young driver and thought that he did an excellent job of driving under difficult circumstances. Hartz was impressed enough to offer Horn a chance to drive his car in the 1936 Indy 500, which he gladly accepted. Hartz, consistent finisher in his years driving the Indianapolis 500, took Horn under his wing. The combination Hartz and Horn was immediately a potent one as Horn would finish second on his first race with Hartz. He had two more Indianapolis 500 starts with the Hartz machine and finished third and fourth respectively.