A view inside the Porsche Type 912 air-cooled flat-12. This engine was used in the 917 race cars and could allegedly produce over 1500hp in qualifying tune. The famous cooling fan on the top is driven directly off the crank.

This engine type powered Derek Bell to 246mph on the Mulsanne and won the 1971 Le Mans 24 Hour with a distance record that was only beaten (by an Audi R15) 39 years later.

Porsche Museum, Stuttgart, Germany.