South African Retief Goosen and Swede Fredrik Jacobson were alone in second after shooting a 61 in the charity event, three strokes in front of Englishmen Ian Poulter and Lee Westwood (61) and Howell and Leonard (67).
Defending champions Perry and O'Hair, who had opened with a 64 in Friday's modified alternate-shot format, failed to maintain that momentum as they slipped back into a tie for sixth at 11 under after a 69.
Kuchar and English were just one under for the day after seven holes but caught fire, posting six successive birdies before adding an eagle and three more birdies over the closing stretch.
Their 12-under score was one shy of the all-time record in the event's better-ball format, Americans John Daly and Frank Lickliter having carded a 59 at Tiburon Golf Club in 2001.
The PGA Tour-sanctioned event features 12 two-man teams with a different playing format for each of the three rounds, and will finish with a scramble on Sunday.
Because of poor weather forecast for Sunday afternoon, officials have moved up the start of the final round to 7:45 a.m. ET (1245 GMT) with the final group scheduled to tee off at 9 a.m.
(Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Gene Cherry)
