At the end, Philadelphia guard Lloyd Free stood in front of his term bench, palmed the basketball and danced the boogaloo of eestacy as the final five seconds ticked off the clock.

"That's right, the boogaloo," he said. "That's what the Celtics did to us when they won the first game here. They humiliated us, and that's what I wanted to do to them. Today was our turn."

It was also Free's turn to lead the one-on-one gang known as the Philadephia 76ers to an 83-77 victory over the defending NBA champion Boston Celtics in the seventh and deciding game of their series.

Although basketball aficionados pooh-poohed the sloppy play in the stretch - Philadelphia shot only 22 per cent in the final period - the 76ers could not have cared less.

They are on their way to a best-of-seven confrontation against the Houston Rockets for the Eastern Conference championship, beginning here Thursday night.

The 76ers advanced mostly because Free, the supremely confident second-year man, never lost faith in his jump shot, although he missed eight of his first 12 shots today.

Free came back into the game with 4:46 to play in the third quarter, and took over. He scored nine of his team's remaining 13 points in the period and set up Darryl Dawkins' lay in.

Free scored 27 points in all, but that torrid stretch left the Celtics staggering to the bench, trailing, 71-63. They never recovered. Free scored the last two points of the period. He missed a 25-footer (a typical shot), gathered in the rebound because no Celtic boxed him out, and scored high about the rim for a follow layup that sent the crowd of 18,276 to slapping hands all round.

Free produced most of his points in the final half against Havlicek, and it was sweet revenge. "He hit me in the face in the last game and broke my nose," Free said. "He couldn't stay with me today. That's what happens when you put a big guard on a quick guard. I knew I could beat him every time I got the ball."

The rest of the 76ers were playing what coach Gene Shue later described as "fantastic defense."

The Celitics hit only 27 per cent of their shots in the final quarter, and had seven turnovers. They finished with 30 per cent accuracy and their big guns were mostly responsible.

Jo Jo White, his every step hounded by Henry Bibby, following a 40-point effort Friday with 17 today on seven-for-24 shooting. He missed all 13 of his second-half shots.

Haylicek, the epitome of Celtic pride and passion, missed 15 of 19 shots, watched a pass bounce off his knee out of bounds at a critical point early in the fourth quarter, and was burned often by Free and, when it counted most, by Julius Erving.

Free left the Celtics woozy at the end of the third quarter, but it was Erving who cold'cocked them for good with 2:48 left to play.

The Celtics had rallied from a 12-point deficit to 81-75 withe 3:09 left, plenty of time for one of those Boston bursts. Then the Doctor's scalpel drew blood.

Erving got the ball down low on Havlicek, wheeled to the basket and put up an underhanded scoop shot for an eight-point lead. It was dancing time.

The 76ers hardly were offensive terrors. Erving, despite his big fourth-quarter basket, missed 13 of 19 shots, and George McGinnis was scoreless after hitting eight points in the first quarter.

Philadelphia was outrebounded, 65-53, although Bibby, smallest man on the floor, got nine rebounds. But the 76ers had 13 steals, and blocked 10 Celtic shots, Caldwell Jones getting seven blocks.

When it was over, McGinnis had a message for anyone who cared to listen. "It's time to give our club credit," he said. "We hung tough down the stretch.Everybody says we don't play as a team. That's a lot of crap. We were the ones who had character, we had pride, and we're going on."

The Celtics showed their class.

Several Boston players came into the 76ers' locker room to offer congratulations, as did coach Tommy Heinsohn, who shook hands with every Philadelphia starter.