Re: Question about connecting rod polishing
It sure looks like a crack to me. I wouldn't run it unless it passed Zyglo inspection. And then I would polish any nicks out. (A nick is the beginning of a crack and a crack is the beginning of a catastrophic failure.)
When I have a part that fails Magnaflux or Zyglo I often do a distructive test to see how close to failure it was. In any case I distroy the part so that it can't be accidentally reused.