Speed was the deciding factor in the Potomac Plate yesterday at Belvedere Farm, even after the field had completed three miles and 14 timber fences. And Frost Time had the speed.

Last year Billy Myers had taken stablemate Donna Donovan to the top immediately and kept the mare there all the way in winning by three lengths. Yesterday Myers waited until the stretch to take Frost Time to the lead and it resulted in another victory for owner-trainer John Myers of the Marlborough Hunt.

"He was content to roll along behind the leader," said 17-year-old Myers. "He wasn't jumping well . . . he got in too close on a couple but I knew all the time he had the speed."

The 7-year-old bay son of Jig Time turned on the speed as the field entered the stretch and eased by Tudorance, which had set the pace most of the way, to win by two lengths. Chick Owens took third place on Inna of Court, slightly ahead of Norm Fraley on Wholesale King.

A claim of interference against John Bosley on Tudorance by Owens was disallowed and Owens had to be content with third.

Inns of Court, which won the Warrenton Hunt Cup last Saturday, was scratched from the earlier Potomac Cup yesterday in Owens' attempt to win the first Governor's Cup race of the season after cancellations at Marlborough, Goshen and Middletown Valley.