The Gilera company was formed in 1909 by Giuseppe Gilera. The company was based in Arcore, in Lombardy, Northern Italy. As the pre-eminent Italian racing motorcycle before the War, it would be the obvious choice for 500 builders. Two engine types were considered:
Rondine 4-cylinder (aka Gilera Four)
Whilst engine width would require an original design for the rear of the chassis, and good ducting to cool the inner pair of cylinders, none of these seemed like insurmountable problems. The 1950-51 version seems to be a remarkably advanced design and would not embarrass in even a modern motorcycle. Four carburettors fed each cylinder individually.
The most obvious use of Gilera engines was in the Volpini – unsurprising as 1951 driver Nello Pagani was a Gilera works rider. Both engines were used, but success was somewhat limited. Although the cars were somewhat heavier than a contemporary Cooper, the main issue seems to have been the lack of fierce competition driving development at a comparable rate to the England. When the cars were sold on, François Antonelli managed to secure a Gilera 4 with his car.
Gilera four mounted in the Volpini
Quite why nobody every seems to have tried to fit this engine in a Cooper will probably remain a mystery......