Yes Absolutely !! you are eligible. In order to secure a seat at a engineering college in Tamil Nadu, you need to clear TNEA (Tamil Nadu Engineering Admissions) exam. The eligibility to sit for the exam is 40% aggregate marks in 12th class in Physics, Chemistry and Mathematics for the reserved category students . Since you have scored over the required percentage you are eligible for taking up engineering.

The cut off marks for TNEA will be fixed by the Anna University to shortlist the candidates for further rounds of the admission process. You need to secure the minimum qualifying marks decided by the university.  Percentage of seats reserved for SC under TNEA :

Scheduled Caste - 15% , Scheduled Caste (Arunthathiyars) - 3%

Please check the following link which contains the cutoff of various colleges that falls under the gambit of TNEA.

https://engineering.careers360.com/articles/tnea-cutoff

All the best !!!