The Hart 420R F2 engine owes much to the Cosworth BDA series, being essentially an aluminium-block derivative using similar heads.

The fruits of this collaboration resulted in Toleman taking a one-two finish in the 1980 European Formula Two Championship.

The Hart-tuned Ford FVA and BDA engines were successful in Formula Two, with Ronnie Peterson winning the European title with an FVA in 1971 and Mike Hailwood taking the same title in 1972 with a BDA.

The arrival in F2 of BMW and Renault left Ford reluctant to increase its involvement, so Hart chose to develop his own F2 engine - the 420R - which was first raced in a Chevron sportscar in 1976.

The off-season of 1978-79 brought the next step in the development of Brian Hart Limited, when the Toleman F2 team committed to providing finance for R&D.