The Paxman Ventura is a diesel engine for railway locomotives, built by Davey, Paxman & Co. The type YJ or Ventura was developed in the mid-1950s as Davey, Paxman's first . With a view to the forthcoming modernisation and dieselisation of British Railways, it was intended as a successor to Paxman's existing medium-speed engine, the . High-speed engines offered higher power-to-weight ratios, which in turn allowed locomotives to have a lower axle loading and greater route availability. The YJ was to have a weight of less than four tons for a 1,200 hp V12, with versions of 8-, 12- and 16-cylinders. Their construction and reliable use though required more sophisticated manufacture than previously, with better metallurgy and balancing of the moving parts for faster running and a stiffer crankc