The valve spring was the Achilles heel of the early OHV engine, and many inventors worked tirelessly to eliminate the possibility of a broken spring ruining an engine. How many inventors? Dozens. Among those auto manufacturers that have use or researched desmodromic systems are Mercedes, Porsche, Fiat, Delage, Cosworth, BRM, Osca, Maserati and Ferrari. The list of motorcycle builders is just as impressive: JAP, Velocette, Neander, Benelli, Moto Guzzi, MV Agusta, Norton, BMW and, of course, Ducati.