Record number of "best director" Oscars won by a single director:

John Ford holds the record with: "The Informer" "The Grapes Of Wrath", "How Green Was My Valley" "The Quiet Man"
Source: New York Times, 7/10/1964

  Most Oscar wins in one year:

"Ben Hur" held the record for 38 years, and still does. It was tied though, by James's Cameron's version of Titantic in 1997. William Wyler, who won for best director with Ben Hur in 1959, worked as an assistant director on the original ''Ben Hur.'' When directing his own version, he gathered his assistants together and wondered which of them would some day direct a remake.
Source: JANET MASLIN, New York Times, , 7/29/1981