 It replaced the Bristol 401 and 402 in 1953 and continued in production for two years.It retained much the same styling as the 401, but featured many mechanical improvements compared to that model.The 1971 cc six-cylinder engine was modified through the use of bigger valves and larger main bearings with a diameter of 54 mm as against 51 mm on the 400 and 401, which increased the power output to as against on the 401.