Dear Mahuabauri

It is difficult to say with certainty as to if or not you will be able to get admission in any AIIMS if you get 80 marks in the exam, which is also the qualifying score in AIIMS MBBS 2018 for SC category. It isn't possible to say anything on this because, AIIMS New Delhi doesn't release the marks of qualified candidates publically, but rather makes only their percentiles available. 

As per the percentile statistics, in 2017 (last year), the lowest percentile in SC category to be called for admission and given admission in SC category was 94.122 percentile. The last rank under this category which got admission in AIIMS MBBS was 17,140 and was admitted to AIIMS Patna. 

AIIMS is a competitive exam. I suggest, instead of looking for how minimum you must score to get an admission, just give your best shot and try to attempt the exam with a clear head, high ambitions and all that you got. 

Wish you all the best!