Following Ford’s withdrawal from Formula Two in the mid-1970s, Hart began designing its own engines. The first engine to bear the Hart name alone was the twin-cam, four-cylinder Hart 420R F2 unit, which appeared in 1976 and powered winning cars until the end of the decade. In 1978, a partnership with Toleman provided finance for further Hart engine development, resulting in Toleman securing a one-two finish in the 1980 European F2 Championship.
Hart entered Formula One in 1981 with Toleman, using an inline four-cylinder 1.5 L turbo engine named the 415T. The initial year proved difficult, with Toleman cars qualifying for only two races. Despite this, the partnership continued, culminating in Ayrton Senna finishing second at the 1984 Monaco Grand Prix and Toleman achieving 7th in the 1984 Constructors Championship. Teo Fabi also secured pole position for Toleman-Hart at the 1985 German Grand Prix, marking one of only two Formula One pole positions achieved by a Hart-powered car.
During the mid-1980s, Hart turbos were also used by RAM (1984–85), Spirit (1984–85), and Haas Lola (1985–86), though none of these teams achieved significant results. Brian Hart gained a reputation for producing excellent work on a limited budget. However, the Hart 415T struggled to compete with the higher-boost engines of major manufacturers like Renault, Honda, BMW, Porsche, and Ferrari after 1984, leading to the cessation of engine development. The engine’s last use was at the 1986 San Marino Grand Prix with Haas Lola, where Patrick Tambay qualified 11th but retired after just five laps due to engine trouble.
At its peak in 1986, with unrestricted turbo boost, the Hart 415T produced a reported 750 bhp (559 kW; 760 PS) at 11,000 rpm, but this was significantly less than the 1,400 bhp of the BMW engines, 1,200 bhp of Renault, Honda, and Ferrari, 1,000 bhp of the TAG-Porsche, and even the 900 bhp of the new Ford V6 turbo. Following the outlawing of turbocharged engines in Formula One after the 1988 season, Hart provided freelance tuning services, primarily working on Cosworth DFR V8s for teams including Footwork Arrows (1990 and 1991), Tyrrell (1990), Larrousse (1991), and AGS (1991).
Hart returned to in-house engine design in 1993 with the 3.5 L V10 1035, signing a two-year deal with Jordan. This partnership yielded a successful 1994 season, with Rubens Barrichello finishing third at the Pacific Grand Prix and securing the engine company's last Formula One pole position at the Belgian Grand Prix. With the introduction of the 3.0 L formula in 1995, Hart developed the V8 830 engine, used by Arrows in 1995 and 1996, where Gianni Morbidelli achieved third place at the 1995 Australian Grand Prix. In 1997, the engines were taken over by Minardi, while Brian Hart designed a new V10 engine, the 1030, but lacked the necessary funding for its construction.
Later in 1997, Tom Walkinshaw Racing (TWR) acquired Brian Hart Ltd., merging it into their Arrows Formula One team. The 1030 V10 was built and raced from 1998–1999 as the Arrows T2-F1 V10, with Mika Salo achieving a fourth-place finish at the 1998 Monaco Grand Prix. Following frustrations with the lack of development, Brian Hart left Arrows.