Just to add a bit more trivia to this thread, there was, sort of, a two-engined car in F1 in the late '60s. In the early-1960s, Formula 1 rules allowed a 1.5 liter engine, and British Racing Motors (BRM) made a flat-8 engine with that displacement. When the rules for 1966 increased displacement to 3 liters, they leveraged their existing work by creating a new engine that was, essentially, one flat-8 on top of another. There was one crankcase, two crankshafts (connected by gears), and four banks of cylinders. It was dubbed an H-16. Later versions had 64 valves!
It was comparable in power to other engines of its time, but at the cost of extra weight and complexity. It did win the 1966 U.S. Grand Prix, in the back of a Lotus 43.