Conversation so far:
When did Juan Manuel Fangio's racing career begin?
He began his racing career in Argentina in 1934
Did Juan Manuel Fangio perform well at the beginning of his racing career?
Following many successes driving mainly modified American stock cars; he was funded by the Argentine Automobile Club and the Argentine government and sent to Europe in 1948.
What type of car did Juan Manuel Fangio drive in the Argentina race?
During his time racing in Argentina, he drove Chevrolet cars.

Question: was he a champion driver?
Self-contained rewrite: Was Juan Manuel Fangio a champion driver?