The car's engine was purpose-built from a hybrid of the Sunbeam Manitou and Sunbeam Arab aero engines, arranged as four blocks of three cylinders in two banks set at 60 degrees. Each cylinder had one inlet and two exhaust valves operated by a single overhead camshaft; the two camshafts were driven by a complex set of 16 gears from the front of the crankshaft. Drive initially went to a rear axle with differential via shaft drive rather than the chains common on competing cars of the period. Suspension used half-elliptic springs all round damped by Andre Hartford friction shock absorbers, and braking was rudimentary — a foot brake on the transmission and a hand brake on the rear drums.
The 350HP made its competition debut at Brooklands in 1920, driven by Harry Hawker, who suffered a burst tyre and spun off the circuit. The differential was subsequently replaced with a simpler crown-wheel-and-pinion arrangement locking the rear wheels together. In October 1920 Rene Thomas set a new record at the Gaillon hill climb, and in April 1921 Jean Chassagne won the Brooklands Easter Meeting 13th Lightning Short handicap at 114 mph.
The car's most significant achievements came in May 1922 when Kenelm Lee Guinness set three records: the Brooklands lap record at 123.30 mph, the land speed record over a mile at 129.17 mph, and over a kilometre at 133.75 mph. This kilometre record was the last land speed record ever set at Brooklands.
Malcolm Campbell drove the borrowed 350HP at the Saltburn Speed Trials on 17 June 1922, recording 138.08 mph — though manual stopwatch timing prevented official recognition. Campbell subsequently persuaded Sunbeam's designer Louis Coatalen to sell him the car, painted it blue, and renamed it Blue Bird, the fourth car to carry that name.
Campbell took Blue Bird to Fano in Denmark on 23 June 1923, recording 137.72 mph over the flying kilometre, but again the timing equipment was not of the approved type. Over the winter of 1923–1924 the car was sent to Boulton Paul at Norwich for wind tunnel testing; the bodywork was streamlined with a narrow radiator cowl and long tapered tail, and the rear wheels gained disc covers.
At Pendine Sands in South Wales on 24 September 1924, Campbell achieved his first officially recognised land speed record at 146.16 mph. He returned to Pendine on 21 July 1925 and raised this to 150.766 mph, the first time any car had exceeded 150 mph. The best single run over the mile reached 152.833 mph.
After Campbell's record runs the car returned to circuit racing with wider tyres and short tail in green paintwork. As late as 1936, bandleader Billy Cotton recorded 121.57 mph over a kilometre on the beach at Southport. The car eventually passed to the Beaulieu collection in 1958 and is today on display at the National Motor Museum at Beaulieu, Hampshire.
During a test fire-up in 1993 to assess condition, a blocked oil way caused the engine to seize and throw a connecting rod, leaving a visible hole in the crankcase for years. Following a complete mechanical rebuild by the museum's workshop team, the Sunbeam was run again in January 2014 for the first time in over 50 years. It was subsequently displayed at Retromobile in Paris and run at the Goodwood Festival of Speed.
In 2015 the National Motor Museum launched a public appeal to fund a new gearbox for the car, as the original had been lost at some point after World War II and replaced with a unit from an Albion 35hp van capable of handling only a fraction of the engine's output. On 21 July 2015, the 90th anniversary of Campbell's first world land speed record, his grandson Don Wales drove the restored car at Pendine Sands to commemorate the achievement.
The Sunbeam 350HP occupies a unique place in land speed record history as both the last car to set a record at Brooklands and the platform from which Malcolm Campbell launched his celebrated nine-record Blue Bird campaign. Its marriage of aircraft engine technology to a racing car chassis set a template that competitors would follow throughout the 1920s, while its survival and restoration ensure that the era of pre-war speed record attempts remains tangible.