Time Benders: World of Adventure Series, Book 14
Super-brain Zack Griffin and hoops fan Jeff Brown wouldn't  normally hang together. But when both boys win trips to a famous  science laboratory, they find out they do have one thing in common:  curiosity. They discover that one of the machines in the lab can "bend"  time--and Jeff and Zack end up in 1334 B.C. Egypt! There's a plot afoot  to kill King Tutankhamen, and the Time Benders have to decide if they  should they save the Pharaoh or just leave well enough alone.