I drive a friends semi truck and trailer to the drag races for him. How many hours can I drive in a 24 hour period We do not haul for hire. Do I need to keep a log book?

Yes to the log book. Even if not for hire, that truck does not fall under any of the FMCSA exemptions, and you're bound by the same regulations are for-hire carriers, including hours of service (11 hours within a 14 hour period which starts counting down with your pre-trip inspection, then a mandatory 10 hours off-duty or in the sleeper berth).