The original 997 cc Mini Cooper engine produced 55 bhp.
The engine was a tuned version of the BMC A-Series four-cylinder unit. John Cooper recognised the Mini’s competition potential, and the Cooper version enlarged the standard Mini’s 848 cc engine to 997 cc. That change, together with twin SU HS2 carburettors, a higher compression ratio and larger valves, raised output from 34 bhp to 55 bhp.
The first Austin Mini Cooper and Morris Mini Cooper arrived in September 1961. The extra power was matched with seven-inch disc brakes, an important upgrade for a small car whose handling encouraged enthusiastic driving. BMC also commissioned 1,000 examples to satisfy Group 2 rally homologation requirements.
The 997 cc figure belongs specifically to the early Cooper, not every classic Mini Cooper. In 1964 it was replaced by a shorter-stroke 998 cc engine. The more powerful Cooper S used different larger-displacement engines, so its figures should not be substituted for the standard early Cooper’s 55 bhp.