2nd two are very good, the first two are potentially brilliant, great depth great fall off great action great colour, you can almost smell the high octane fuel, feel the shail as they burst past, ears rattling..
Like these two an awful lot, but... I know you are using a big prime lens here, I just feel the crop is too severe, obviously if its the out the box composition you are stuck, if it's a later crop I would consider giving it 10% more space around the frame so as not to clip the helmets or the wheels.
For sports stuff I like to try and find an end compostion that I can let the camera pan to and then rest, I need the pan to let my aiservo start doing it's stuff ahead of the burst, I just get the feeling here that you've been tracking and lost focus on the composition slightly.
I'm being very critical here, hyper-critical, on the cusp of being ridiculously unreasonably critical, it's just that I love the first two images so much for everything else, if they were 10% wider they would just be absolutely perfect.