The Chicago Cubs' delirious dream of a pennant may have come to rest on Sheffield Avenue this afternoon.

That's where four of Philadelphia's six home runs finally stopped bouncing as the rapacious Phillies won their ninth straight game, 10-3.

The reeling, injured Cubs, who led the National League East by 8 1/2 games in July, now find themselves four games behind the Phils in mid-August.

This balmy day, with a breeze blowing out, was to be a showdown of aces, with the NL's two leading winners - Chicago's Rick Reuschel (15-5) and Philadelphia's Steve Carlton (17-6) - going head-to-head. That lasted less than three innings.

In the second, the Phillies battery of Carlton and his personal catcher, 18-year veteran Tim McCarver, set the tone. McCarver lofted a wind-aided fly into the right-field screen for a solo homer and pitcher Carlton followed with an enormous two-run blast over wall, ivy, bleachers and back screen into Sheffield Avenue for a 3-0 lead.

Before the day was out McCarver was 4-for-4 at the plate, with two homers and more total bases in one game (10) than he had ever managed in a career that dates to 1959. Carlton, now the majors' leading winner, finished with a resolute, unchallenged seven-hitter.

Greg Luzinski, Jay Johnstone and Tommy Hutton also joined the carnage with homers. "Watch out for the Bull," said the headline in the local afternoon paper here. But Luzinski, the torrid Bull, was watching out for himself, crashing a three-run shot halfway up the bleachers to the opposite field for a 6-2 lead that broke the game open in the third.

Just two pitches after Luzinski's 30th homer, Johnstone curled a liner around the right-field foul pole to knock out Reuschel. The Cub righty, who had allowed only eight previous gopher balls all year, watched four fly over the right-field fence in two-plus innings.

Cub reliever Pete Broberg also spun his head toward Sheffield Avenue twice as McCarver and Hutton made it unanimous: all six Phil blasts (equalling a club record) disappeared to right field.

Nevertheless, the Phils fear that this opener of a four-game series may have been a Pyrrhic slaughter. Fool-hardy Philadelphia center fielder Garry Maddox crashed into the umpteenth wall of his career, suffering a "first-degree separation of the right shoulder at the point of the collarbone" which will keep him out three-to-four weeks.

The injury to "The Mighty Burner, as Maddox is known, had a double irony. First, without the .278-hitting Maddox, the Phils' outfield of Luzinski, Bake McBride and Johnstone will have a higher average than before - .322, ,315, .310 from left to right. Second, Maddox, who smashed into a wall and sidelined himself earlier this year with the score 10-1, damaged himself today on a grab with one out, no one on and a five-run lead.

"Garry's run into a lot of walls," said Phil manager Danny Ozark. "That ivy makes it look soft and comfortable out there, but it's brick underneath. There's a lot of leaves, but it's the hardest wall in baseball and the most dangerous.

"If our fence in Philly was concrete, we'd have a second Pete Reiser," added the somber Ozark, referring to the Brooklyn center fielder of a generation ago who, like Maddox, lacked the normal human deference toward solid barriers.

The Phils are rolling in such grand style that Maddox's absence may not faze them. "Momentum is the most important thing in sports," said Mike Schmidt, "and the hardest to talk about. But one thing is for sure. We have it now. Other teams' homers curve foul, ours blow into the first row. You don't explain it. You just go with it and milk it as long as it lasts."

As befits a team riding on mighty "Mo's" back, the Phils got typically unexpected help today.

Carlton's homer ran a personal hitting streak to 7-for-9. In his next atbat he reached first on a catcher's interference.

"They're afraid of me," he said with a laugh. Carlton, normally known as one of the easiest men in baseball off whom to steal, picked off two runners. "New move," he explained. "Learned it from Jerry Koosman (New York Mets). I grabbed him in the outfield before the game one day and wouldn't let him go until he showed it to me."

McCarver, his average now up to .319, seemed a perfect example of what momentum can do. "I guaranteed Hutton before the game that I'd get three hits." McCarver said. "I thought I was kidding. He hits a homer and I get two homers in one game for the second time in 18 years.The second one . . . I couldn't have hit it any harder."

McCarver admitted he would have quit baseball three years ago "except for my inability to take the uniform off. LIke a lot players, I just couldn't say the words, 'I quit.'"

Old friend Carlton requested that the Phils get McCraver, saying the veteran receiver settled him down and understood his pitching patterns. In the 2 1/2 seasons since McCraver has been "Carlton's baby sitter", as they say in clubhouse vernacular, the left-handed Carlton has turned from a 44-47 pitcher (1973-75) to a 37-13 hurler.

"They even call us the W-a-a-a-h Brothers, said McCraver, making the sound of a baby crying.

Today it was the Cubs and a house of 38,011 (28,849 attendance is the paid figure) fans that cried. The Cubs, who face the three best teams in the league - Philadelphia, Pittsburgh and Los Angeles - in their next nine games, have an astounding injury list with Ivan DeJesus and Jerry Morales the latest starters out of the line-up.

"If we could just play .500 ball until Bruce Sutter (star reliever) gets off the disabled list on Aug. 26," said ex-Cub Ernie Banks today. "The subs have to keep us alive until we get healthy."

But today six balls flying toward Sheffield Avenue made the beloved Cubs chances look very sick. "Sorry, Ernie," teased Phils coach Tony Taylor, "but we're here to take four straight. Nothing else will do."

Even Banks, always the last to be discouraged, just looked away and shook his head. The all-too-familiar reality of Cub life had been brought back to mind again. Six times.