Simplify the following text for a Grade 7 native English-speaking person.
Original: The Offenhausers won five straight victories at Indianapolis from 1971 to 1976 , and it was not until 1981 that they were eliminated as competitors by engines such as the Cosworth V8 engine .
Simplified: The Offenhauser engines won five straight races at Indianapolis from 1971 to 1976 . It was not until 1981 that engines such as the Cosworth V8 engine eliminated them .