There was a bigger radial than the R3350, Pratt & Whitney built the R4360. Four rows of 7 cylinders if you ever hear for the " corn cob " radial they are talking about the 4360. The B-36 bomber had 6 of them the KC97 tanker had 4 as well as the B-50 bomber. The very last model of the F4U Corsair WW2 fighter had one as well. If you really want to see some cool old engines the Udar Hazy Museum at the Dulles airport has a big display of engines as well as devlopment history. I think the airforce museum has like one entire hangar dedicated to powerplants