Keith Blaynee, who raced Imp variants in the 60s and 70s built an Imp V8 engine in 1974 (or so). He used it for events, but it proved unreliable (maybe). It had a throw of about 1½ inches and would rev to well over 13 thou. But as the body was too narrow for the engine, it had to be split lengthways and had to have about 6 inches welded in. It made it look really low and racey.
He was well into Imp engines. He built racing engines as well as trial ones, like David Carr's. Several Imp engines for Autograss competition were built by him. And he was heavily involved with using Imp engines for speedboat racing. He had also built one into a motor bike.
Keith passed away in March 1990.
The Imp Site