After taking a half to shake the cobwebs out of their smooth-functioning running game, the Los Angeles Lakers turned on the power in the third quarter and stunned Philadelphia, 124-117, in the opening game of the NBA championship series tonight.

Game 2 in the best-of-seven series will be played here Sunday at 1 p.m.

The Lakers, who hadn't played in 12 days since sweeping San Antonio in the Western Conference finals, outscored the 76ers, 19-2, in a 5:09 stretch in the third quarter that turned a 15-point deficit into a two-point lead and quieted the sellout crowd of 18,276 at the Spectrum.

Philadelphia appeared to be in a state of shock as the fourth quarter began. As they realized their best chance of beating the favored visitors was slipping away, the 76ers scored one point in the first six minutes and fell behind, 105-90. That meant that the Lakers outscored them, 40-9, while coming back from an 83-68 deficit to a commanding 108-92 advantage in a stretch of 10:21.

Jamaal Wilkes, who scored 16 points in the decisive third quarter, and Norm Nixon led the Lakers with 24 points. Kareem Abdul-Jabbar had 23. Julius Erving led all scorers with 27 points.

"I thought the layoff bothered us for a while," Los Angeles Coach Pat Riley said. "We were out of synch for a while. But we stayed with our trapping defense and forced them into an open-court situation. That's our strength."

Wilkes made 11 of 22 shots and got seven of his 10 rebounds off the offensive boards. He seemed to be in the right place all night to capitalize on the 76ers' defensive breakdowns.

"Jamaal just keeps working," Riley said. "He's continually moving and getting in position to get layups off the fast break. Magic (Johnson) is a great passer and he looks for Jamaal a lot."

In the last six minutes of the third quarter, when the Lakers turned an 83-68 deficit into a 91-89 lead, Wilkes scored 10 points on three fast-break layups, two free throws and an 18-footer.

In the first 3:12 of the fourth period, when the Lakers outscored Philadelphia, 14-1, Bob McAdoo made six points. He finished with 14 points as all seven Lakers who played scored in double figures.

"We're a team of spurts," Riley said. "We've done that all year. Sooner or later we're going to make a move like we did tonight."

The difference in the two halves was quite apparent. In the first two quarters, the 76ers were shooting well and getting a lot of baskets off offensive rebounds. After intermission they committed 12 turnovers, which led to 15 points for the Lakers, and lost control of the boards.

"We played very well for 2 1/2 quarters, then we broke down," Philadelphia Coach Billy Cunningham said. "Both teams are so explosive that a 10-point lead doesn't mean as much as with other teams. Once we got behind, we just couldn't come back."

This game brought back memories of the first game of the Eastern Conference finals, when Philadelphia lost by 40 points. The 76ers also squandered a 15-point lead while losing Game 6, but still bounced back to beat Boston in seven games.

While Wilkes was getting out on the break and receiving a lot of passes, Nixon was getting just as many points by controlling the ball. The 6-foot-3 guard finished with 10 assists.

"In the first half, we didn't run well, convert the break or keep them off the boards," he said. "Our defense definitely had something to do with our comeback. We created turnovers and turned them into baskets."

After six ties in the first seven minutes, Philadelphia took a lead it was able to maintain until the Lakers' great surge late in the third period.

Erving scored six points in the first three minutes, then Andrew Toney (20 points) and Darryl Dawkins scored eight each in the period.

Rookie Kurt Rambis, the odd man in the Lakers' lineup of four all-stars, had eight of his 12 points in the first quarter, including the last four that cut the 76ers' margin to 32-30.

The 76ers scored the first six points of the second period to boost their lead to eight points. Riley called time, and the Lakers came back behind Michael Cooper and Nixon to close within a point. Philadelphia then outscored the visitors, 13-3, with Erving getting four points and Bobby Jones three to strengthen its lead to 61-50 at intermission.

After Bobby Jones opened the second half with a tap-in, Erving scored six straight points and the highly partisan crowd was on its feet screaming.

When Caldwell Jones made a devastating dunk and Toney followed with a long jumper to increase the lead to 83-68, it seemed like it was the 76ers' night.

That's when the Lakers woke up. That's when they showed the crowd and a national television audience how they were able to win 57 regular-season games and eight straight in the playoffs. That's when they gave the first indication that this might be a very short series.