The Class 55 Deltics are no longer in BR service, having been withdrawn around 1980 but there are nutty railway club types who collectively own 1 or 2 and run 'em on private track. The Napier deltic engines are almost certainly still in marine use although the engines are no longer in production.
As for the 14 cylinder,25,000 litre Sulzers, these are built in situ inside huge ships and servicing work is carried out from the inside of the engine. These are still in use day in day out. Strangely the're very fuel efficent too, far more so than a road diesel. I suppose at 102rpm there's not a lot of friction compared to 5000rpm.
It's the five and a half million lbft torque that's the really silly number. As if 100,000 bhp is tight either.........
These are truly monumental engines, you can't really comapre them to car engines.
Another interesting car is 'Chitty Chitty Bang Bang' from the film of the same name. (author Ian Fleming, yes - the James Bond man!)
Despite it's cultured and characterful image I'm led to believe that it was powered with a 23 litre Maybach aero engine.
As such, it probably went very nicely indeed.