According to 'Modern Motor Cars', Volume 1, A. W. Judge, Caxton Press, London 1921, pages 124-5 (see below), an ohv engine was originally available. However a side valve engine of 85mm bore and 114mm stroke (1300cc) was put into the first production cars, itself being soon superceded by one with the stroke increased to 121mm (1370cc).
In 1922, despite a £40 price-cut, sales were slow (and were not helped by a moulders dispute and the emergence of the Austin Seven) and a further '10% off' offer was made in October.
In 1924 Belsize Bradshaw production ended. Total Bradshaw production records were never found. Engine numbers 735 and 2039 exist which suggested there was a production run well into the thousands although some engines were used in solely 'stationary' applications.
Further reading: "Motor Sport", May 1960 page 346; "The Automobile", Feb 1984 pages 28-32; "The Automobile", Oct 1989 pages 50-53; "The Automobile A-Z of Cars of the 1920's" by N Baldwin, 1994 page 41 (ISBN 1.870979.532); "The Complete Catalogue of British Cars" by D Culshaw and P Horrobin, MacMillan, London 1974 pages 76-78 (ISBN 333.16689.2); "British Car Factories from 1896" by P Colins and M Stratton, Veloce Publishing 1993 page 92 (ISBN 1.874105.04.9); "The Beaulieu Encylopedia of the Automobile Volume 1" by N Georgano (editor), HMSO page 145 (ISBN 0.11.7023191).
Thanks to: Barry Collins, Information and Archive Officer, Coventry Transport Museum, www.transport-museum.com, 024 7683 2425; Nick Forder, Collections and Information Department, Museum of Science and Industry in Manchester, www.msim.org.uk, 0161 606 0127.