Hot Water, the car using the airplane engine is a 27-Litre Bentley. I believe it uses a Merlin engine. It has been on Top Gear before, along with Brutus, which is powered by a BMW airplane engine. These automobiles resemble 1920s/30s racing cars, but they were probably built for fun. There's also a Packard-Bentley powered by a 42-Litre boat engine, named Mavis.
Well, it's too bad that it isn't possible for a prime mover to power an automobile, but at least the idea sounded interesting enough to ask you guys.