Dear friend,
There are some private colleges that give admission only on the basis of the marks you get in their entrance exams.
They do not consider the marks of JEE Mains.

But no engineering college will give you admission solely on the basis of 12th standard board exams.
You will have to appear for their entrance exams and pass those exams in order to get a seat in that engineering college.
Following are some of the college which provides you admission in engineering course are given as below:--->>

1.BITS,Pilani
2.Thaper University,Punjab
3.BIT,Patna
4.NSIT,Delhi
5.IMSEC,Ghaziabad
6.AKGEC,Ghaziabad
7.GLBITM,Noida
8.Galgotia University,Noida
9.Nagarjuna college of engineering,Banglore
10.ICET,Delhi
11.J.P University,Solan
12.RET,Jaipur
13.SKIT,Jaipur
14.Satyabama,Chennai
Good luck !!!