McKeon clocked a personal best 52.29 seconds in the blue riband 100 metres freestyle to top Cate Campbell's year-best of 52.43 at last month's national championships on the Gold Coast.
It was another win over former world champion Campbell, who McKeon beat for the title on the Gold Coast. Campbell was second in Sydney on 53.27 seconds.
"It gives me confidence racing the mornings and I’ve just got a lot stronger and done a lot of work in the gym. That’s where I think I’ve made big gains,” said McKeon. "And every time I get to race Cate and be up against the best in the world it adds to my confidence and it’s just good race practice."
Teenager McKeown clocked two minutes, 4.31 seconds in the 200m backstroke for another year-best time. McKeown is shaping as a major threat for American world champion and fellow 19-year-old Regan Smith, who holds the world record of 2:03:35.