The ELIA TITANO is 4cc(.25)and long stroke like most side port of that period (1946) so it will swing a large prop with more pitch than a glow equivalent at a much lower rpm. Ma first diesel engine(a long time ago)was a French Stab 1.25cc and it was swinging a 10"X6" without problem on equal parts of ether/Kerosene and castor oil!