Want to change post excepts style in Eleven40 Genesis Child theme

Hello I’m using the latest version of genesis and latest version of wordpress. Along with genesis i’m using Eleven40 child theme (Not Pro theme, the old one)in my http://allindiatalks.com .

I enabled the option “show post excerpts” but latest is post is showing full length in this child theme by default. I mean the post which we publish lastly will be shown full content and rest of all post shown as excerpts.. This feature came default with theme..

But I don;t like that i want normal look for example: parent genesis theme.. It would be helpful if you tell me the code need to be changed in theme files..