Simplify the following text for a Grade 12 native English-speaking person.
Original: Bugatti , Duesenberg , Alfa Romeo , Mercedes-Benz and Miller built successful racing cars with high-performance dual overhead camshaft straight-8 engines in the 1920s and 1930s .
Simplified: Bugatti , Duesenberg , Alfa Romeo , Mercedes-Benz and Miller built successful racing cars with high-performance straight-8 engines in the 1920s and 1930s .