"The 16 had canted inlet valves which made the trumpets sit on a distinctive slant. This allowed the necessary room for the larger Bosch fuel injection system which used two 908 pumps placed end-to-end.
Only four complete engines were made, although parts for up to ten might have been made. Porsche was serious about winning with the old 917 platform and drafted up a complete car with a working flat-16 engine. Enough horsepower was made available, but that wasn't enough to match the scalability of the turbocharged cars.
Mark Donohue tested that car at the Weissach track and said it was a real monster. He got the impression that it could be turbocharged up to 2000 bhp.
The decision to go with turbo charging was the right move. Five-liter flat-12s produced up to 950 bhp and helped George Follmer win the 1972 championship. Later versions of the turbocharged Porsches were the most powerful cars ever raced.
Only a sole 16-cylinder prototype remains and it's currently retained by the Porsche Museum. Only one other complete 16 cylinder engine is retained by the factory"