Even before 5-foot-11 guard Michael Porter outdueled four taller competitors to win easily the halftime slam dunk contest, yesterday's 12th McDonald's Capital Classic had become a showcase for the little men.

It was the play of Porter, from Dublin, Va.; Quin Snyder of Mercer Island, Wash., and Kenny Wilson of Jersey City that allowed the U.S. All-Stars to break open the game in the final two periods en route to a record 142-120 runaway over the Capital All-Stars before approximately 10,000 at Capital Centre.

This 2 1/2-hour epic was not one of the better played Classics. The teams committed a total of 56 turnovers, were called for 52 personal fouls and missed 118 shots from the floor.

The U.S. team scored 89 points in the second half in setting a record for most points in the Classic. The 1976 U.S. team had set the record in its 138-107 victory.

But despite the periodically sloppy play, several players had good games. Coolidge's Tim Anderson, the most valuable player for the Capital team, ended with 20 points and 11 rebounds, Spingarn's Sherman Douglas had 24 points and four assists, and All Saints' Phillip Gamble and Cardozo's Earl Moore each had 15 points.

Two-time all-America Danny Ferry of DeMatha had a horrid afternoon for the Capital All-Stars, making only three of 10 shots from the floor and three of seven from the line for nine points. He also had only five rebounds.

"The ball just wasn't dropping," he said. "I tried to play aggressively but I just haven't played well in front of big crowds the last two times (including the city championship at Cole Field House)."

The visitors, who had a decided height advantage with Houston's 7-1 Tito Horford (16 points, seven rebounds, five blocks) and 6-11 Doug Roth of Knoxville, Tenn. (five points, six rebounds), controlled the rebounding in the second half. What surprised the locals was the quickness of the U.S. team. Three guards, Rick Calloway of Cincinnati (24 points, six rebounds), Ed Horton of Springfield, Ill., (21, nine) and Walker Lambiotte of Woodstock, Va., (eight points), helped their side force turnovers, slip inside for second and third shots and beat the Capital team for fast break baskets. Calloway and Horton were the U.S. team's most valuable players.

"We were able to dominate the inside and came up with key rebounds," U.S. Coach Bill Fox said. "We got the ball to the wings, who were having an easier time getting good shots. What worked best for us was the slam dunk."

Thanks to a few slams and good guard play by Douglas and Moore, the locals trailed by only 53-48 at halftime. The deficit still was five following Douglas' jumper with two minutes gone in the third quarter.

But the overall strength and speed of the U.S. team began to take a toll.

"We felt we were just as quick as they were," said Porter, who had 10 points, 10 rebounds and five assists.

Anderson said the difference was on the backboards. "I tried to get inside for rebounds," he said. "They didn't box out, but they were taller."

The 6-8 Horton, who scored 15 points in the third period, muscled his way inside for seven points, Porter maneuvered through traffic for three baskets and the 6-6 Calloway had five points in helping the U.S. team to a 92-82 lead after three periods.

The U.S. team really put heat on in the final quarter. Snyder (eight points, five assists) and Wilson (11, six) got their team running and the Capital All-Stars couldn't keep up. Calloway made a jumper and two layups, and Toney Mack, who averaged 41 points per game the past season, scored consecutive baskets as the U.S. lead swelled to 20 with four minutes left.

In the preliminary game, Mount Vernon's Tracy Scruggs made a 14-foot jump shot with eight seconds left in overtime to provide the Suburban All-Stars with a 101-99 victory over the District All-Stars.