If you're using unreal engine 4, here's a great free car pack to get started.

https://www.unrealengine.com/marketplace/en-US/product/bbcb90a03f844edbb20c8b89e...

Let me know if you need help setting it up. I'd love to help build the environments/tracks/levels/cars. Some of my work is here. https://mobile.twitter.com/HomeFireGames

Could you explain a bit more about the kind of racing game you have in mind?