It was as if a barn door had been flung open and the pent-up horses had finally been allowed to run wild.

After they had been slowed to a walk in their semifinal series with Washington, the Boston Celtics were turned loose by the Philadelphia 76ers Sunday and they're eager to continue running in Boston tonight in the second game of the NBA Eastern Conference final. The game will not be televised or broadcast on radio in the Washington area.

"We're a much better team when we can run," said Nate Archibald, whose ball-handling and passing usually dictate the pace. "We have a lot of guys who like to get out on the break and we're more effective that way. That was our style during the season."

The Celtics won 63 regular-season games by outrebounding and outrunning their opponents and they hope to use the same formula against the 76ers. None of the players expects a repeat of Sunday's 40-point debacle, but confidence is soaring in the Celtics' camp.

Boston's big advantage is the inside play of Robert Parish and Larry Bird, who combined for 48 points and 29 rebounds in only 70 minutes of the opening 121-81 blowout. Unless Darryl Dawkins' sore leg makes a miraculous recovery, the 76ers won't have the manpower to combat the Celtics' talented twosome.

Dawkins' status still was uncertain after the 76ers practiced yesterday. The 6-foot-11 center worked out and said he would try to play. Coach Billy Cunningham said he hasn't decided how much he'll use Dawkins, although the coach needs all the rebounding he can get.

In addition to Parish and Bird, the 76ers have to contend with reserves Kevin McHale and Rick Robey around the basket. Playing half the game, Hale scored 16 points and grabbed 11 rebounds. In only 19 minutes, Robey contributed 19 points and six rebounds, five offensive.

Robey played well in the opening game of the series against Washington, scoring 10 points and grabbing five rebounds in 15 minutes. But he finished the five-game series with only 24 points and eight rebounds.

"I hope Rick can keep it up," Boston Coach Bill Fitch said. "This is the way he started the Bullets series."

Despite playing only 29 minutes, Parish exceeded his season average in all three categories when he scored 24 points, had 14 rebounds and blocked seven shots. Just as in the Bullets series, he was Boston's most valuable player.

"I worry about Parish more than anybody," said Bobby Jones, who always emphasizes defense. "He's blossomed into such a good player."

Cunningham obviously has matchup problems. He opened this best-of-seven series with Caldwell Jones guarding Bird and Dawkins against Parish. Jones fouled out in 12 minutes trying to stay with Bird and Dawkins couldn't handle Parish.