Harley-Davidson debuted the Knucklehead in 1936 and millions of subsequent Big Twins built in its image continue to "potato-potato" down the road! Technical Editor Kevin Cameron and Editor-in-Chief Mark Hoyer talk about the origins of Harley-Davidson's EL and journey through the Panhead, Shovelhead, and up to the modern era. Think of it as the engine that grew with the American highway system! Join us on the ride!