Revising Titles

I currently have 61 posts in my blog, and each one has its own short unique title. Since they are short, I’m thinking of adding some more key phrases to the titles to strengthen their appeal to viewers. I plan to do this by just adding a few words of text following a hyphen that I would put at the end of each of the current titles. If I make such a revision on my titles, will this damage or in someway hamper the display of these titles by search engines? How would such a revision in these titles affect their listing in my site map and categories? I want to strengthen the appeal of my posts, but I don’t want to create new problems or confusion in their display or listings. I would just like to add some new information about each post into the title tags without changing the text in each post. Please let me know if it would be OK to do this. Thanks.