Turn a corner and he suddenly appears, a dark apparition standing all alone and out of place in the hot California sun. A bulky man in a black, baggy suit and clunky shoes, an undertaker or hit man, lighting a long, long cigar. Sylvester Stallone is getting ready.

No one knows what he's thinking, people know better than to even approach when he's so into himself, but if he has any sense of history, any sense of romantic, Stallone is letting the nuances of the day, the wheels inside of wheels, flow through his mind.

He is standing in the middle of what used to be David O. Selznick Studios, where "Gone With The Wind" came into being. His hair has been slightly thinned and greyed at the temples, because like James Dean in 'Giant' he has been artificially aged a quarter of a century. Like Brando in "On the Waterfront," he is soon to have a crucial confrontation with Ron Steiger. And like any other hot phenomenon he is probably wondering if he's covered all the angles, if he's made the choices that will enhance rather than exterminate his career.

In his first film since a modest item called "Rocky," Stallone has chosen to play Johnny Kivak, a truck driver who, in the timeless words of the publicity in material, "climbs out of the streets become the most powerful labor leader in America," to specificially become the head of F.I.S.T.," the Federation of Interstate Trucks.

Inside the large, dark sound stage that Stallone is facing, a rectangle the size of a railroad boxcar is the only source of light. Inside the rectangle is a perfectly reproduced office of a United States senator, complete with a blowup of the Capitol dome outside the window. It is the office of Senator Andrew Madison, played by Rod Steiger, who is determined to clean up Kovak's union.

For half of the morning, director Norman Jewison, a busy business-like man who wears a F.I.S.T. button on his cap, has been inside the box with Steiger and Stallone, rehearsing. The scene in question will last something like three minutes on the screen, but it is essential one, may times rewritten, and what with entrances, exist, closeups and retakes, it will take all day and more to film.

Stallone, as Kovak, enters the office with a heavy step, his voice tired, like Caruso with a head cold, worn out, as he says earlier in the film, by "too many cigars, too many meetings, too many lots of things."

He tells Steiger's Sen. Madison he came to make a deal, that he wants him 'stay out of my union." Madison quietly asks if he thinks he's "too big for the United States Senate," and Kovak slowly growls back, "You don't represent the people, you represent yourself, ambition, money . . . old money. You smell, I'm sorry, you stink of the establishment." This is too much for the senator, who lets it known, as only Rod Steiger can, I'm going to get you, and I'm going to get every other piece of dirt there is and put them away for good." Which, except for a final dig by Kovak, is where the scene ends.

Seeing this, and knowing that one of the alternative endings planned for the film is Kovak's violent death, it is impossible not to think that the life of teamster leader Jimmy Hoffa is in some way being evoked. Yet Jewison takes pains to deny this, saying, If we want to do a Hoffa film, we would have done it, we would have called it 'Hoffa,' He's not the only labor leader."

A spokesman for the International Brotherhood of Teamster in Washington said yesterday that the film was not being discussed at his office, and that he knew nothing about it.

As to what Stallone thinks about all this, it is impossible to say, for the erstwhile man of the people has apparently seem one person too many. When location filming started in Dubuque, the self-proclaimed "second cleanest city in Iowa," Stallone had said, I'm not like some actors, I don't hang out in trailers, I like to talk to people." But that was months ago.

Now the strain of public life, plus the strain of a 19 weeks shooting schedule that will finally end with three days of exterior shooting in Washington beginning Friday, has worn him down. "He feels like 'geez, can't I just

"Not only is it stretching me artistically," he says all in a rush, "but it's a history lessons, in entertainment form. Films of this nature, massive subjects that encompass world-wide areas, labor, Hitler, Napoleon, are coming to an end. I also wanted to touch working men, giving them a sense of history, an idea of the fundamentals in their backgrounds, so when they walk out of the movie theater they feel cleaner." End of the interview.

The Washington filming will culminate in a major scene in which Kovak, the powerful labor leader, emerges from Senate Investigation Committee hearings a broken man. The script calls for thousands of truckers, who have gathered in Washington to announce their support for their leader, shouting in unison "Give 'em hell, Johnny."

Other shots will include trucks driving and through the city past the Capitol and the White House. The story is set 1957 and period street scenes will be reconstucted with senators' cars, taxis and trucks from that year. The film is scheduled to open at Easter.

If Stallone is reticent, Norman Jewison makes up for it. Intrigued by the American labor movement, its radical origins and its conservative denouement , he has been wanting to make it the basis of a film for almost 20 years.

"The idea is to follow the struggles of a working man through the past figure." the director says, visibly excited. "We deal with strikes, idealists, things that went together to weld America, that were part of the fabric."

More than this, Jewison is fascinated, as he hopes audiences will be, by power and the struggle for power. What "The Godfather" was all about. The corruption of power has always been a classic theme," and if "F.I.S.T." has echoes of "All the King's Men" as well as "On The Waterfront," it's hardly accidental.

Long-standing interests or no, Jewison found the major studios reluctant to do a labor film. "Most studios like to steer away from anything that smacks of controversy," he explains. "When I wanted to do 'In the Heat of the Night,' they backlash. When I wanted to do 'The Russians Are Coming,' everyone told me it was a bad idea, that there was nothing funny about the Reds. With the subject matter is that commercial.' Nobody wanted any trouble."

Making the difference, aside from Joe Eszterhas' script, was Jewison's being able to "honestly say that none of my pictures have lost money. I'm cynical when it comes to power and you only have power if people come to see your films. The most important fact is that I'm financable."

And let's not forget about Stallone, who Jewison had seen in "Rocky" before it went nationwide. 'I had a verbal, handshake deal with him before its release, and though he was later offered twice the money to do other things, he kept his word. He remained completely committed to the idea that this should be his next picture, that it was rich, that it had something to say."

As befits a man whose 14 films have been nominated for 26 Academy seems to have "F.I.S.T.," you'll pardon the expression, well in hand. Except for one little detail. He's not at all sure how it's going to end.

I've shot one ending and I'm going to shoot at least one more; I've never done that before," he admits. "In one, Kovak dies, in the other you know he's going to meet an unpleasant end but you don't actually see it. And then we have a possiblility of keeping him alive. The film will tell me what to do in the editing process. When you're dealing with a story of epic proportions, it's nice to have that possibility. It's not like writing a book. You can't just reach for another piece of paper; you have to shoot it beforehand."

And since this will be in a sense a serious film, a film of ideas that intends, Jewison says tentatively, "to make you think a little bit," the director has some additional over-riding concerns.

"I don't want to make a dull film, God, there's nothing worse than a dull, boring film," he says with someheat. "And I don't want to make a film small groups are going to screen for each other. Spending two years of my life on a film which nobody comes to see would be a disaster, the worst thing in my life.

"I don't give a f--- what critics say, I don't care if they say 'don't worry, Norman, it's brilliant, the Cinema Theque Francaise says it's brilliant, Pauline Kael says, 'the last vestiges of film art are in your hands.' I can't stand that elitist approach to film. It's a popular art and unless that audience is there, film is a dead thing, just a lot of cans on the shelf."

Yet, Jewison can't help being you to fight an often unequal battle with all the fluffy, fun stuff. Later that day, for instance, he picks up a Hollywood Reporter and notices with distaste a two-page ad touting the through-the-roof grosses of the light-hearted "Smokey and the Bandit."

"Look at this, 32 million bucks," the director says, momentarily beside himself. "And we sit around trying to figure out how to make something that says something." And with on flamboyant gesture, he tosses the newspaper into a nearby trash can. Thus ever the tyrants, etcetera.