Moonee Valley specialist Sweet Emily outsped her rivals in scoring a record-breaking victory on Saturday.

The four-year-old, ridden by apprentice Harry Coffey, became the fastest horse over 1000m at Moonee Valley when clocking 57.19secs, taking 0.03 secs off the record held by Miss Andretti.

But Sweet Emily, a winner of two of her previous three starts at Moonee Valley, had to survive a protest from the runner-up Beach Front, ridden by Stephen Baster, over alleged interference at the 500m.

Stewards said they couldn't be satisfied that the interference was greater than the winning margin of a long neck.

Sweet Emily, who had run third at her previous start at Moonee Valley over 955m, which had followed successive victories at the track over that trip, appreciated the extra distance, according to trainer Phil Sweeney.

Sweeney said the mare will be kept to races at 1000m and longer now.

"The 1000 metres suits her better. There's a lot of pressure in those 955 races," Sweeney said.

Coffey said he was surprised the mare had broken the track record.

"That's how good she is," Coffey said.

"You don't think you're going that quick on her.

"When you're on her it just feels like you're cruising."