Jim Morrison drove in seven Pittsburgh runs with a triple, a double and a hotly disputed grand slam as the Pirates jolted the Los Angeles Dodgers yesterday, 12-3, in Three Rivers Stadium.

Morrison's fifth-inning homer off Tom Niedenfuer made it 9-2 and touched off a 10-minute argument, Dodgers Manager Tom Lasorda arguing that Morrison, rounding first base, passed runner Tony Pena.

Pena was standing a few feet off first, watching the ball fall into the left field seats as Morrison, running with an eye on his drive, appeared to pass him. Morrison quickly retreated and retouched first as Dodgers first baseman Greg Brock and third baseman Bill Madlock began screaming at first base umpire Lee Weyer and Lasorda charged out of the dugout.

The umpires let the home run stand after huddling in private for about two minutes. Television replays of the incident were not available. Weyer said as the ball was hit to left, he started toward second base.

"They said Morrison passed him, but you have to see it to call it," Weyer said. "If I'd seen it, I would have called it. I don't know if he went by him or not."

"Everybody saw it except the guy who was supposed to see it," Lasorda said.

Madlock said Morrison "had a sheepish look on his face" as he retreated to first, but neither Morrison nor Pena would admit the umpires missed the call.

"He touched me but he never passed me," Pena said.

Morrison said. "I think I went up the base line . . . more than I did run around him. I don't think I passed him. I don't want to say much about it because I've been in a slump all season and I just want to enjoy this."

Morrison would have been given credit for a single if he had been called out, but the three runners would have been permitted to score.

"What difference is one run?" Madlock asked. "So it's 11-3 instead of 12-3. But what can you do? I respect them the umpires more when they tell the truth. If he didn't see it, that's it."

Morrison, whose previous high was six RBI in a 1984 game against the New York Mets, put Rick Rhoden (4-3) ahead, 1-0, in the second with an RBI triple off Bob Welch (3-5). He got a two-run double in the fourth. Needing a single to hit for the cycle and two RBI to tie the Pirates' record, he struck out his last two at-bats.

"I chased some pitches," he said.

*Phillies 16, Padres 5: In Philadelphia, Juan Samuel's three-run double and bases-empty homer and Glenn Wilson and Darren Daulton's three-run homers overpowered San Diego in the Phillies' sixth straight victory.

Philadelphia's 16 runs, a 1986 league high, came with 12 walks and 15 hits off five pitchers, helping Steve Carlton (4-6) win although issuing five runs on 10 hits in six innings. For the first time since September 1984, the 318-game winner has won two straight.

*Cubs 7, Braves 3: Gary Matthews' Wrigley Field wind-blown, two-run triple capped a three-run Chicago first inning against Atlanta and winner Guy Hoffman pitched his first career complete game, an eight-hitter.

Matthews lifted a fly to right field that got caught in the 31-mph wind blowing in and eluded Billy Sample. "The craziest fly ball I've ever seen. It went three different ways," Cubs Manager Jim Frey marveled, " . . . but if the wind had been blowing out, it would have been a three-run homer instead of a two-run triple."

*Cardinals 2, Reds 1: Danny Cox, an 18-game winner last season, got St. Louis' game-winning RBI and his first victory of 1986 with outstanding relief from Todd Worrell at Cincinnati.

Cox (1-4) singled home the tie-breaking run in the second inning, coaxing a slow roller through the right side. He left after the fifth with a tight right elbow. He had given up six hits, one an RBI single by Pete Rose.

The Reds filled the bases in the seventh and eighth, but Worrell bailed Pat Perry out of the first jam and himself out of the second one with third-out fly balls.

*Astros 8, Expos 4: Bob Knepper became the league's first nine-game winner and Glenn Davis homered and drove in four runs as Houston won at home.

Knepper (9-2) pitched six innings and gave up four Montreal runs on six hits, including Andre Dawson's 10th and 11th homers and four RBI. Knepper tied Boston's Roger Clemens for the major league lead in victories. Dawson became the all-time Expos home run leader with 216, one more than Gary Carter.

*Giants 7, Mets 3: Mike Krukow, the winning pitcher against Dwight Gooden 10 days previously, beat previously unbeaten Ron Darling (6-1) as San Francisco capitalized on five Mets errors in New York.

Krukow (7-3) retired the first nine batters, extending his streak against New York to 32 consecutive batters faced without allowing a hit. He went 7 1/3 innings this time, allowing seven hits. One was a two-run homer by Ray Knight, whose wife, golfer Nancy Lopez, delivered their second daughter on Memorial Day.