My experiment websites

Recently I have been working on a plan. It is experimental and I am not very sure about the results. I am sharing the experiment with all of you hoping that you may help me. I have four websites of my own and i use exactly same number of words in all of them. I maintain the keyword numbers and total word numbers too. Every time I change someting on a site, I repeat that in other sites too so that the word count remain same. Now my doubt is, Search engines may mark them as duplicate. Can anyone tell me what should I do.