1927 Delage racer

For the GP class of 1922 Louis Delage ran a 2 litre V12. This car did very well but when the formula changed to 1.5 litre class in 1926, the company built a DOHC straight 8 engine fed by 2 superchargers.
 For 1927 it was developed further, one supercharger was removed, but the 170 hp undersquare straight 8 with 5 speed transmission was still the dominant car, so much so that it was still competitive a decade later.