The argument to [HttpRequest.setTimout][1] is a millisecond value so for 2 minutes:

    req.setTimeout(2 * 60 * 1000);

**PS** With the clarification that the desire is to make the web service call after a 2 minute delay I suggest you experiment with this https://salesforce.stackexchange.com/questions/37310/need-system-schedule-cron-string-for-run-once approach. In your case you would build the cron string to be 2 minutes from the current date/time.

  [1]: http://www.salesforce.com/us/developer/docs/apexcode/Content/apex_classes_restful_http_httprequest.htm#apex_System_HttpRequest_setTimeout