Get a new domain , if you build anything other than what the last site had , it will take longer for google to clear its cache ....
BTW , you can send a message from google webmasters to google ,requesting them that you want your site to reconsidered for crawling (when you do that , just delete everything from your site and place a simple html page or wordpress)... this might help you in a faster google cache clearing , and then you can start your porn site on the same domain ...
Note - it usually takes a week or two for google to respond to your request and most of the times , they dont mind reindexing your site as if it were a new site -- you just need to request them ... also telling them that you'll be opening a porn site on the same domain wont be a good idea (IMO)