Much as we like flathead engines, Detroit's development of V8s with overhead valves after World War II really gave a shot of horsepower to those speed-maddened hot-rodders who were ready to take their machines to the next level past the ol' flathead Ford. Cadillac and Olds came out with their sibling OHV engine design in 1949, and Caddies from that year until 1967 were powered by 331s, 365s, 390s, and 429s. Plenty of these engines found their way into hooned-out Model Ts and As as well. Engine photo credit: Stephen Foskett [Wikipedia]