ITS A muggy and blistering hot Saturday afternoon in Washington. But Stacy Lattisaw, 13, is racing around the Kenilworth Avenue go-cart track, the sun freckling her ruddy skin and lightening her golden brown hair.

At $1 for five laps, Stacy is winding around for the 30th time. She has enough tickets for 30 more laps but her mother begs, "Stacy, you can save those tickets. We don't want to be out here all day."

She shrugs okay and walks away from her go-cart. But even heading for lunch at McDonald's with her family, she can't leave the fast track.

In her father's red Cadillac, the radio is turned up loud and tuned to a local pop station that announces that the next record has just hit the charts and is a smash -- the most requested single in the city. It comes from an LP to be featured in that night's album spotlight. The song begins: a light, heart-thumping disco tune called "Dynamite." The voice is strong, with an innocent sexiness.

Stacy's 8-year-old-brother, Jerry, weary from standing in the sun, suddenly stands up beaming in the back seat.

"That's my sister Stacy's record," he says and settles back as her voiced is pumped out of the backseat speakers: Cause you move so sweet When you're dancin' Got the beat Got the heat Like dynamite It's dynamite . . .

Stacy Lattisaw stares out of the car window.

Suddenly Stacy Lattisaw is a hit vocalist who was scheduled as the opening act for the Spinners' concert last night at Carter Barron Amphitheater. It's a teen-age dream, but Stacy shrugs it off with genuine adolescent unconcern.

She just is not fazed by the fact that her May-release single, "Dynamite," produced by Marada Michael Walden for Cotillion Records, jumped 70 points last week on Europe's pop charts and moved up 25 points to No. 33 after entering Billboard's top 100 two weeks ago. It is 25 with-a-bullet in Cashbox and 27 with-a-bullet in Record World.

When the BBC strike is over, Cotillion wants her to go to Europe for singing spots on television in Holland, Germany and Britain. She just signed with the William Morris agency, which is booking her in East Coast summer tours with the Spinners and Smokey Robinson, and negotiating another with George Benson. A big co-promotional poster in record stores zooms in for a close-up of her with Bill Cosby who signed it: "This is my oldest personal friend in show business."

But Stacy, who just finished eighth grade across the Anacostia River at Sousa Junior High, looks blank when asked if she is excited about her hit album, meeting celebrities and jetting off for Hollywood talk-show tapings between math and phys. ed. classes.

"I guess so," she offers.

"All she wants is 10 or 15 kids in the yard. You see I don't have any grass out there," Stacy's mother sighs, standing in the small kitchen that overlooks a dusty plot in the back yard. "If she could sing and never leave home, she'd be happy."

According to her mother, Stacy doesn't like airplanes, gets homesick easily -- even though the longest she's been on the road so far is about five days -- and frankly would rather spend her time racing go-carts, swimming or playing Spades.

Success, it seems, has not spoiled Stacy Lattisaw.

It's understandable, Success snuck up on her. It came as a combination of luck, timing and circumstance: a virtual show-biz miracle in which a 13-year-old from Southeast Washington got a five-year contract on Atlantic Records' Cotillion label and all the money and glory afforded by hits such as "Dynamite" and her new album "Let Me Be Your Angel."

Stacy's father, Jerome Lattisaw, works for the U.S. Government Printing Office. Her mother is not employed, and keeps house in a simple home facing a condemned building across the street. They had no friends with political or entertainment connections to introduce Stacy to the "right" people. There weren't even any singing or dance lessons. Stacy cannot read music.

Her producer manages a simple, obvious explanation of the success surrounding her: "Talent."

"I used to sing around the house, and when Stacy was 6 or so she started singing along. Before I knew it, she was outsinging me," Saundra Lattisaw says of her plump, green-eyed daughter.

"When she was about 10, her sister asked her to sing at the Spingarn High School homecoming and she said she didn't want to, I said, 'Will you sing if I pay you $5?' You know, she got up there and sang and made that $5!"

Within 18 months Stacy had made the rounds singing at all the fashion shows and amateur talent nights in town. Then she was asked to open a free National Park Service Show headlined by Ramsey Lewis. An estimated crowd of 30,000 at Fort Dupont Park went wild, loved her, hollered for more. c

She did five songs. Her father taped them.

Frederick Knight, then a producer with TK Records, was urged to listen to the tape by Al Dale, the Recreation Department official who organized the show. Knight thought the 11-year-old singer was "fantastic." He offered her a contract and meanwhile started writing a song inspired by her youthful outlook.

The contract with TK Records was rejected by a family lawyer familiar with the recording business. The lawyer, meanwhile, dialed up an associate of his -- the president of Cotillion Records.

Without ever hearing a note, Henry Allen, Atlantic Records senior vice president and president of Cotillion Records, asked Lattisaw and her parents to visit his New York office.

"When I realize someone we knew was interested in her, I asked her to come to New York," Allen says. In November 1978, "They came up -- Stacy, her mother, father, little brother -- with no tapes, no pictures. Nothing."

Allen rented a studio that same day, called in the rhythm section of "Mass Production" and heard Stacy Lattisaw sing for the first time. She instructed the group to play Debbie Boone's "You Light Up My Life."

She started singing with the same kind of passion and fever that made it a hit for Boone. Everyone stopped, they say, and listened to the sweet but powerful young voice laced with professional, vocal timing and sexy phrasing no one expected.

Allen offered her a contract with Cotillion Records on the spot.

In the spring Stacy recorded her first album, "Young and In Love," produced by Van McCoy. A jacket full of oldies but goodies, it was a commercial flop.

Meanwhile, an unknown schoolteacher named Anita Ward was enjoying a phenomenal burst of success that could have been Stacy's if she had stuck with TK records and recorded the song she inspired Frederick Knight to write: "Ring My Bell."

"She was a young kid, had a very young voice," Knight says now from his office in Jacksonville, Miss., where he heads Juana Records. "And you know how kids are -- they like to talk on the phone. When I started writing "Ring My Bell" I was referring to the telephone. When I started working with Anita Ward I kept the title but changed, matured the lyrics."

At 13, Stacy has plenty of time to make up for missing last summer's biggest disco record. Her contract with Cotillion calls for her to make two albums a year for the next five years.

"The average adult needs a steady flow of hits," Allen says, adding that the public will be looking for Stacy's next record, whether it be this year or two years from now, just as they did with the very young Michael Jackson.

Cotillion orginially promoted the single and album on soul stations in big metropolitan cities with large black populations -- Washington, Memphis, Detroit, Chicago, Los Angeles. Her first tours this summer will be in those cities, dates Stacy hopes will only be on weekends.

"She's gonna make a lot of money," Allen says. But her mother confides that Stacy doesn't even have $8,000 in the bank for a sports car she'd like to buy someday.

Cotillion is paying most of her professional expenses now, and trying to make up for money lost on her first album. The amount she'll make from the current single and album has not been determined yet. But tours such as the one being negotiated with George Benson could earn her up to $6,000 a performance. In one week she could earn more than her father makes in a year.

A school counselor observes that many of Stacy's friends and schoolmates cannot believe how she is reacting -- or rather not reacting -- to the possibility of a future so bright that many with the same chance often get lost in the glare.

"They feel that if they had the opportunity, they wouldn't think to keep on being one of the crowd, not taking the spotlight," the counselor says.

Teachers, girlfriends, family agree: Stacy is still the same -- still shy, quiet, very low-key. Her publicists at Cotillion Records are quick to caution how shy she is and fret about interviews and personal apperances that call for her to speak.

Seated on a Hollywood set next to Dinah Shore recently, Stacy was quiet and polite. Shore asked her, "If you had a chance to meet any celebrity you wanted, who would it be?"

She immediately bubbled with the youthful adrenalin usually reserved for her high-energy stage performances.

"Michael Jackson," she said.

Shore continued, "If you had a chance to date any celebrity you wanted, who would it be?"

Again, "Michael Jackson."

Back in Washington, she allows that Michael Jackson is her favorite entertainer. "He's supposed to be calling me this week," she says, perched on black awning steps in front of her house. "Just to say hello," she adds, above the giggles of two girlfriends waiting to go go-cart racing with her.

However she reacts to interviews, Stacy has no shortage of enthusiasm on stage. She flirts with the audience and her band, jumps to the beat and dances with the same kind of energy she uses to throw her voice out over the audience.

Once offstage, the shyness is back. But it seems that her downcast eyes, simple yes-or-nor answers and sideways glances are less the result of shyness than a response of being only 13 in a whirlwind of adults who sometimes expect her to be what most stars are: witty, talkative, extroverted balls-of-fire.

"When you work with a 13-year-old, it's easier," producer Walden says. Established recording artists may dismiss your ideas or disagree on major points, according to Walden, but with Stacy "I have total surrender. Whatever I asked her to do, she tried to give it to me."

In her album "Let Me Be Your Angel," Walden (who composed the songs with lyricist Bunny Hull) gives Stacy a repetoire of material basically marked with his style of syncopated downbeat rhythms. The title tune is a ballad, but the others are moderate-to fast-paced formula, disco numbers. The lyrics generally deal with partying and having a good time.

"I tried to keep in mind what is going on with a 13-year-old," Walden said, acknowledging that one doesn't write the same kinds of songs for a Donna Summer as one would for a Stacy Lattisaw.

"The album is definitely a crossover," according to Cotillion's Allen, who reports that it's getting much air play from New York's biggest pop station, KTU-Radio.

"She has something most black artists don't have," Allen says, "a worldwide hit."

Yet for most in the recording business, Allen warns, "You're only as good as you next record."

Stacy is not concerned about that.

Asked if she wants to make a million dollars -- and what she would do if her success fizzles out -- she heaves her shoulders and sighs, as if to say "Who cares?"

But she politely answers.

"I don't know."