Hey Doddi! 

You at least need 99 percentile or above to get a call from IIM-B. While if you have done graduation in any arts subject, you will get call from IIM-A at 95 percentile also, under the academic diversity quota. Whereas, in case of IIM-C, they give more importance to work-experience. In case, you have 60 percentage in engineering, your chances of making into IIM-A, B and C is less. So, various other criteria’s work in the final selection after CAT. Right now, what you can do is clear CAT with your best of preparation and aiming 99+. Even, if not the old ones, you will easily make into new IIMs. Best wishes!