That SB6…
..Rolls Royce built and experimental engine for it, a whopping 36 litres and designed to output a massive amount of power.
Rolls Royce shelved it as too radical. They built the Merlin, which powered the Hurricane, Lancaster, Mosquito, early Spitfire and the P-51 Mustang.
Later, they dusted the racing engine off, engineered it for reliable running and fitted it to Spitfire prototypes in the early 1940s. It became the Griffon and by the end of the war was outputting a staggering 2,250hp reliably in production form in the Spitfire Mk21. For comparison the early Spitfire 1a and Hurricane 1 output around 990hp.
The Griffon finally left RAF service in 1990 when the Shackleton (itself a development of the Avro Lancaster/Lincoln line) was retired.