The Pittsburgh Pirate baseball family took a giddy communal bath in Great Western champagne today to celebrate their victory in a Great Eastern Pennant race.

"Way to go, you dirty Bucs," bellowed little Phil Garner, atop a locker-room table, a bottle of bubbly in one hand and a foot-long cigar in the other. "What're we going to do to Cincinnati?"

"Kick their butts," came back the chorus from the Pirates, who now head to Cincinnati for Tuesday's National League playoff opener against the Reds.

This was great race day in Pittsburgh, and prize day at Three River Stadium.

While 7,500 people were jogging through the town, and others were winning horses and motocycles at the ballpark, the folks who really received all the gifts today were the Pirates.

The Bucs put an end to their six-month marathon of endurance with the Montreal Expos by accepting a 5-3 win handed to them by the gracious Chicago Cubs.

An even bigger present, however, was Philadelphia's 2-0 victory over the Expos, thanks to a left-handed Santa Claus named Steve Carlton who struck out a dozen Montrealers in his shutout.

The Pirates, tied with the Expos in the lost column at game time, needed both a victory and a Montreal defeat to break out the champagne. Far more likely, it seemed, was an Expo makeup doubleheader in Atlanta on Monday, and perhaps even a one-game playoff in Montreal on Tuesday.

But this was Christmas for the Pirates. Every time they turned around, somebody was trying to give them something.

Of the five Pirate runs, three were given to them by the Cub defense, while a fourth resulted from an egregious umpiring call that might have become a part of controversial lore if this had ended as a one-run game.

Whenever the shaky Buc starter and winner, Bruce Kison, got in a deep jam, the Cubs handed him a crucial double play -- four of them in the first five innings.

When Pittsburgh was clinging to a 3-2 lead in the seventh inning, and desperately needed a couple of insurance runs to support reliever Kent Tekulve, the Cubs rose to the occasion.

With the bases loaded and two outs, the Pirates Bill Robinson hit a sickly grounder to the right side. But Cub second baseman Mick Kellerher let the ball trickle off his glove as a pair of gloriously needed runs scored on the "hit."

Finally, came the greatest gifts. "The magic number is one!" exalted the scoreboard at 4:05 p.m. when Montreal lost.

Just 15 minutes later, Tekulve, making his 94th appearance and saving his 31st game, put an end to his three-inning stint, and to this interminable pennant race.

"I couldn't wait for it to end," said Tekulve, who got two quick strikes on the last Cub, Bruce Kimm. "I tried to throw him a 500 mph slider and just bury him.

"Naturally, the only thing it hit was the backstop. So I just calmed down and threw him a normal nasty slider."

Kimm's feeble popup came down, symbolically, in eactly the same spot -- about 40 feet behind third, right on the foul line -- as the last out of the great pennant race of '78 between Boston and New York.

"I did my victory shuffle," said Buc third baseman Bill Madlock, one of many Pirates who invented a new dance step. "It'd take everybody in this room to get that ball away from me."

The Pirates, a team that swings between genuine jubilation and well-disguished depression, was slightly subdued in victory, compared to the splendid lack of inhibition that might have been expected.

"This has gotta be hell for the Expos," said Dave Parker, who showed his mettle with homers Thursday and Friday, then eight hits in the season's final two games. "We think we have the best personnel in baseball, but you gotta respect the way Montreal just wouldn't let us go."

The only dry Pirate, the one man nobody sprays with anything, was the team captain, Willie Stargell, patriarchial goat on Saturday who characteristically rebounded today with his 32nd homer and a sacrifice fly.

"A thing of beauty," Stargell muttered. "This was the best of 'em. No comparison," said the 38-year-old who has been on five previous Pirate division titlists in the '70s. "We did today what we've done all year -- whatever it takes."

Equally true is that the Cubs, and umps, did whatever it took to keep the Pirates ahead.

In the first inning, left fielder Dave Kingman, who later hit a solo homer (No. 48), misplayed a Parker single, allowing Tim Foli to go from first to third, from where he scored on Stargell's fly. Actually, what Kingman did was get hit in the groin by the ball and collapse in a heap after tossing it back to the infield.

Kingman was hardly alone in this day of injuries. Kison was blasted in the shin by a liner and left the game after six innings because of an ugly-looking blister on his middle finger.Home plate ump Bruce Froemming was kayoed for a few seconds by a deflected pitch that conked him in the left ear. Cub Bill Buckner played with a finger brace after being hit with a throw.

It was another multiple collision, however, that might have gone down ignominously in baseball history if this game had been a one-run Pirate win. It taints this game enough, as is.

Leading off the Pirate fourth, John Milner, the Hammer, laid down a dainty drag bunt to pitcher Lynn McGlothen's left. The 200-pound McGlothen is graceless at the best of times. Later in the game, he fell off the mound in mid-pitch, landing in a lump at the foot of the mound.

This time, McGlothen snagged the ball in the tip of his glove, made a lunging tag on Milner's backside, swatting him squarely with the ball while he was 10 feet short of the bag. McGlothen then collided with first base ump Jerry Dale, and even smashed into the Cubs' first base coach -- in effect, tagging everybody in sight.

The crowd of 42,176 had a good laugh, then an ever better one as it realized that Dale had called Milner "safe," believing that McGlothen had missed the tag.

If ever a play called for instant replay (which was clear) or four-ump consultation, this was it. Dale was not only in a bad line of vision but got bowled over on the play.

But Milner stayed on first, reached third on a Madlock single and scored as Cub second baseman Kelleher bungled what might have been a tough inning-ending double play ball on a grounder that was generously scored as a RBI hit for Garner.

The Pirates willingly accepted all gifts today. They have had one brutal extra-inning game, or marathon doubleheader, or exasperating loss, on top of another. Fittingly, this win gave the Pirates 25 victories in their last 36 games for a season total of 98 -- their highest figure since 1909.

It hardly diminished Pittsburgh's clutch finish that they won two out of three this weekend from a Cub team that has played 12-24 ball against the Bucs and Expos and has lost 27 of its last 40. So what if Cub outfielder Larry Bittner lost a ball in his hat this week? He thought to look under it eventually.

"Don't relax now," whispered Pirate sub Mike Easler to Parker. "We still gotta go to war."

"We leave Monday morning for Cincinnati at 9 a.m.," hollered Garner, still on his table, still puffing his cigar. "It's our first-time-ever charter."

"What kinda charter is it?" asked one sarcastic Buc, accustomed to Pittsburgh flying commercial, "A charter bus?"

The Pirates laughed. "To Be Real" shook the locker room with its disco beat. Parker crept up behind sub Lee Lacy and built a huge mound of shaving cream on top of his Afro. Lacy, proud of his towering crop of hair, never felt it. The dirty Bucs laughed louder.

The Great Western was consumed just as the Great Eastern already had been. Slowly, dizzily, happily, the Pittsburgh Pirates were gearing up to go to war once more.