French-bred Manco Capac II won the 56th running of the Middleburg Hunt Cup in ridiculously easy fashion today, making believers out of those who thought the 9-year-old gelding would wilt carrying 160 pounds over the 3 1/2 mile, 18-jump course.

Rated beautifully by the nation's top steeple chase rider, Tommy Skiffington, Manco Capac II covered the distance of Virginia's oldest timber steeplechase in 6:38.2. 2.1 second faster than Still In All posted here last year. Manco Capac II ran second by three lengths in that race.

Myrmidon led from the 10th jump until Skiffington took his mount to the top at the 16th and finished second. Devil's Brolly was third and Bottom Button fourth.

The early leader, Travelling Son, fell at the 12th fence.

"Ladies hunter competition, that's where he is going," said George Ohrstrom Jr., the chestnut's owner . . . that's what he is now." Others had visions of a meeting between Manco Capac II and Barros Negros in the Virginia Gold Cup on May 7.

The latter won the Virginia timber horse of the year award over Manco Capac II in balloting earlier this week.

Manco Capac II had raced in France, Broken down and was brought to this country as a hunter for Ohrstom's children. Trainer Bunny Deeds turned him in to a timber horse and sent him out to win three out of four starts under her daughter Diane in the recently completed point-to-point season.

It was 19 years ago this month that Ohrstom won the Middleburg Hunt Cup with another French import, Fast.

Joe Aitcheson Jr., the oft-retired steeplechase champion, showed he still retained the magic touch, riding Machu Picchu to a seven-length victory over Conserje in the co-featured James L. Wiley Memorial before a sun-baked crowd of about 7,000.

Another impressive performance in a day of impressive victories was turned in by Mrs. Samuel Bogley's Sabinus in the Middleburg Business Community Plate. Bruce Fenwick rode the speedy 10-year-old former hurdle campaigner to a length victory over Bel Esprit II in the three-mile maiden timber race. It was the third consecutive victory over timber for Sabinus, the other two coming on the point-to-point circuit.