E31 BMW M8: 30 Years Ago It Made 640 horsepower

The E31 BMW M8 Prototype is arguably one of most valuable concept cars in BMW’s portfolio. The one-off is not only a priceless prototype, but also one of BMW’s best engineering achievements. In 1990s, the legendary Paul Rosche developed a 6.1 liter, naturally-aspirated V12 engine, dubbed the S70.