Vincent Black Shadow high temperatures at the track that year. Big-end failures put an early end to the attempt but several records were achieved including the 6 Hours and 1000 Kilometres by a Black Shadow. One of the spare engines for the run at Montlhéry wound up in Vietnam. It was sold to an owner in the United States, who installed it in a Rapide frame. The bike changed hands several times before being bought by Herb Harris and restored to Black Shadow specifications. Vincent Black Shadow Motorcycles produced by Vincent H·R·D at their factory in Stevenage, Hertfordshire, England were renowned for their
Vincent Black Shadow engine's ports. Early Black Shadows have a third inner valve spring not shared with the Rapide, but this feature was dropped from later bikes. Due to the low-octane 'Pool' petrol that was all that was available in the early post-war years, bikes of the period could have only low compression ratios. Although the prototype Black Shadow was built with a compression ratio lower than the Rapide's nominal 6.8:1, production Shadows have a ratio of 7.3:1 due to having different pistons from the Rapide, although still supplied by Specialloid. The Black Shadows have different carburettors than the Rapides, with Series B