Denis Potvin put the first goal of the Stanley Cup final into his own net tonight. The New York Islanders' captain found the right target on two other occasions, however, and his score at 4:07 of sudden-death overtime carried New York to a 4-3 victory over the favored Philadelphia Flyers.

Potvin had to share the hero's role with referee Andy Van Hellemond, who never will win a popularity contest in this town because he choose to officiate by the rule book rather than by tradition.

Both Potvin's game winner and the tying goal by Stefan Persson with 3:42 left in regulation time were scored with the Flyers shorthanded. Tradition says that penalties other than murder and maiming will be overlooked in the third period and overtime of crucial Stanley Cup contests.

In fact, NHL statistics freak Ron Andrews asserted that Potvin was the first man to score a power-play goal in overtime in a Stanley Cup final since such records were first compiled in 1934.

The sinning Flyer was defenseman Jim Watson, who grabbed John Tonelli and threw him down as Tonelli was skating toward the goal. It was a blatant penalty, yet Watson protested the call and Potvin admitted he did not expect to see Van Hellemond's arm raised.

"In overtime we figure we can cheat a little bit and the ref might not call it," Potvin said. "But that was such an obvious penalty. Our guy had the puck and was going for the net and he pulled him down. He almost had to call it, but I have to admit I was surprised when he did."

Only one second remained on Watson's penalty when Potvin skated into the slot, took Tonelli's pass from behind the Philadelphia goal and drilled the puck past goalie Pete Peeters.

"He laid one of the most beautiful passes you'll ever see," Potvin said. "He had to lift it a couple of inches to get it over a stick. I saw the open ice in front and I positioned myself for a pass and Johnny saw me and put it there."

Flyer fans were celebrating when Rick MacLeish caromed a shot off the side of goalie Bill Smith's left leg into the net for a 3-2 lead with 6:50 remaining in regulation time. Moments later, MacLeish had a breakaway that might have clinched it, but Smith stood his ice and MacLeish fired the puck off his chest.

With 5:25 remaining, Flyer Al Hill hooked Garry Howatt to the ice and Van Hellemond did not hesitate to blow his whistle. On the ensuing power play, Mike Bossy sent a fine pass from the right-wing circle to Persson skating swiftly in from the left point and Persson fired high into the far corner of the net.

The Islanders collected three power-play goals in five chances, demonstrating that their extra-man maneuvers are more dangerous than those of the Flyers' three previous opponents, Edmonton, the New York Rangers and Minnesota.

Philadelphia yielded only eight power-play goals in 77 opportunities to those teams. Coach Pat Quinn feared the Islanders, though, to the extent that the sellout crowd of 17,077 saw some startling examples of self-control by their usually ill-tempered heroes.

In the first period, New York's Bob Nystrom dealt a solid check to the usually pugnacious Moose Dupont, then shoved Dupont's helmet down over his eyes. Dupont merely adjusted the headpiece and skated away.

Early in the second period, former Capital Gord Lane skated into Flyer penalty leader Paul Holmgren and poked a glove in his face. Holmgren backed off.

"In the first period, you could feel the tension," Potvin said. "It was incredible. Both teams were very cautious and everybody was freezing up. There wasn't as much hitting as we expected, but I don't expect this series to turn into a violent charade. It's going to be won on breaks and work. We have too much respect for each other for it to be any other way."

Earlier in the evening, there was little reason for Potvin to expect to become a hero. Even before the game started, during the warmup, he tripped over the cage and fell, drawing razzberries from the crowd.

It got worse, Midway through, the first period, the Flyers' Mel Bridgman tried to jam the puck from behind the net. He fell and Smith, flopping to the ice, made the save. The puck was still loose, however, and Potvin, in trying to poke it under Smith, sent it across the goal line. Seeing his error, he actually leaped over Smith in an effort to pull it back. s

"I did get a lot of gals, didn't I?" Potvin asked later, when he could laugh about it. "Smitty made a great play coming back, but the puck lay between his legs and he didn't know where it was. I wanted to put it under him, but the puck found an opening and it trickled over.

"I thought the puck was dead long enough to blow the whistle, but Van Hellemond disagreed."

Bossy tied it 11 seconds after a trip by Bab Dailey gave the Islanders their first power-play opportunity. Then Potvin drilled the puck past Peeters' waving glove on a setup by Clark Gillies for a 2-1 New York advantage.

After Peeters foiled a breakaway by Bryan Trottier, kicking his left leg out to block a backhander, Bob Clarke pulled Philadelphia even on a power-play deflection of a Bill Barker slap shot.

MacLeish scored once, but not the twice that might have been expected, and the Islanders were able to celebrate their fifth victory in six overtime contests this year.

"We don't like overtime, but if we have to play it we want to win," Potvin said. "Our conditioning is as good as or better than anybody's in the league and we just work until we score."