The other day @booster916 was talking to me about why we have the racecar frame sandblasted every year. This is why.
Looking at it you say it is just bare metal. That is not true though. Sandblasted metal rusts at a very very slow rate. Cracks in the frame will show up within a day and look like this.
That is where our motor plate bolts too. If it breaks loose it is bad news bears.
We found about 3 cracks in the frame that are getting welded up tonight then she heads to paint on Friday.