Every day here has felt like Friday the 13th to the unloved, underrated U.S. boxing team.

First, unlike the ballyhooed 1976 Olympic team that won five gold medals, this U.S. squad arrived as a distinct underdog to Cuba. In fact, predictions were that the U.S. might lag behind Puerto Rico in medals.

If the last U.S. Pan American Games team had the likes of Sugar Ray Leonard, Howard Davis and the Spinks brothers, this one was high-lighted by little '75 Pan Am gold medalist Davey Armstrong.

Armstrong immediately went out and lost his first fight.

"The public threw it on us real quick that, you know, we weren't too good - not close to the Cubans," said light welterweight Lemuel Steeples. "So we took it on our selves to prove "em wrong."

Then, the 11-member U.S. team got a peek at their "plush" living conditions in the Pan American Village - no air-conditioning in one smallish suite of three bedrooms and one living room.

"Cramped up together like we are, we can't do nothin' but get along with each other," said classy bantamweight Jacke Beard. "If we ever got to arguing in that little place and a fight broke out, it'd be every man for himself."

Finally, the team arrived at the 4,000-seat sweatbox Coliseum in the center of the winding hillside barrio of Trujillo Alto. It made their apartment look spacious.

Their locker room was a two-toilet men's room with the door torn off its hinges. Fighters from 33 nations, usually a dozen of them a night, used the one-room "facility."

In that room, full of blood, tears and a nervous tension like a silent storm cloud, the U.S. team began looking inside itself - and finding victory after victory.

Where the Cuban team had trained together for years on its national-squad farm outside Havana, the U.S. team found its togetherness in that small room where fighters took turns retiring to the relative seclusion of those two toilet stalls to meditate in the final minutes before the bell.

Outside, the rabid Latin crowds cheered madly for any Puerto Rican and rooted partisanly against most gringos. "Down here, you don't want to leave nothin' up to the imagination of the judges," Beard said. "You have to leave 'em no choice."

So, the Americans began leaving no choice, night after night. Usually, the Cubans suffered.

Perhaps the U.S. calling card was delivered by the team's grizzled veteran - featherweight Bernard Taylor, who, at the age of 22, has had an incredible 410 fights. Feathers aren't supposed to punch hard, but Taylor, a silver medalist in the '75 Pan Am Games and a member of the '76 Olympic team, flattened Cuban Angel Herrera in the first round.

No sooner had Cuba lost one near-certain gold then light heavyweight Tony Tucker, a statuesque 6 feet 4, won a smart tactical decision from Cuba's Sixto Soria to divest them of another. Soria had won silver at Montreal, losing only in the finals to Leon Spinks.

Now, as Saturday's finale arrive with matches in all 11 weight categories, which nation has the most finalists, and the best chances for the most gold?

The U.S., with six guaranteed, bonded silvers already in hand - more than half the team in the finals.

"We took our inspiration from the '76 Olympic team," said Beard, the 5-foot-4 muscleball who, at 17, has nine years in the ring and over 100 fights behind him. "At the end of this week, it won't be Cuba on top anymore. It'll be the U.S.

"Not braggin' on the Cubans or nothin', but they all hit hard. On the other hand, they all fight the same - straight-up punchers who aren't that hard to hit. They'll be lucky to take second place from Puerto Rico."

Saturday night - the Pan Am show-closer - should be a war, with Cuba having placed five finalists and Puerto Rico four.

The Americans will not look pretty, like Sugar Ray Leonard, as they tape up their hands in their narrow room. These are not glamor boys, heavy favorites. Everyone has paid his way to the finals with cuts and bruises. They are survivors.

Of the final sextet of Beard, Taylor, Steeples, Tucker, paperweight Richard Sandoval and light middleweight James Shuler, perhaps the best symbol of the group is Shuler, from Philadelphia's Joe Frazier Boxing Club. He is in the finals on will alone.

Twice he has won decisions by 3-2 margins, first over Cuban Luis Martinez, then Thursday night over Dominican Jorge Amparo. In that last fight, Schuler was bleeding over both eyes throughout the final round, but swarmed Amparo every time he could see him.

The browd booed the decision, not knowing that judges are supposed to be blind to blood and only see the number and quality of punches. "Sure, I won," insisted Shuler, both eyes semiclosed. "Every punch he hit me with, I hit him back the same, only harder.

"I felt a funny feeling, like a nerve, go all the way up my head through my scalp, so I figured I was bleeding. I saw all the red on him, but I didn't know it was all coming from me.

"This is my first cut. . . my first two cuts. I just kept pressing him; that's for a fact."

"The left one's okay. The right one we'll have to sew up," murmured a doctor to the U.S. trainer.

"Yeah, yeah, that's fine. The guy he's fightin' (in the finals) is nothin'," said the trainer, presumably for Shuler's benefit.

"Yeah, he's nothing. He won't crowd me. I'll be all right,c said Shuler, presumably for his own benefit.

Every U.S. finalist has stitches, but Shuler, Beard and Tucker have the worst - all over their eyes. And they are the three who must face hometown Puerto Ricans in their matches, natives who throughout these Games have gotten away with butting and raking with the strings.

"There's been a lot of dirty fighting down here," said Steeples. "The referees are letting a lot go. But we've mad it this far."

When the professional money gets handed around after the Olympics, it's unlikely that this U.S. team will get rich. Beard and Tucker have the tools to go furthest, with Tucker, 21, perhaps the best bet for cash on the line as a heavyweight.

Even here, game but mediocre heavywight Rufus (Bubba) Hadley has monopolized the publicity with his comic victory prediction over Teofilo Stevenson - a bravado move that his Cuba-hating mates liked.

When a stateside reporter called the U.S. delegation press office here, Hadley answered the phone and said, "Hello . . . no, he's not here, sorry . . . But you can interview me."

The six Americans in a hunt for gold here, with more to come in Moscow, also slow with a quip and long on lumps. They may sleep in their own sweat - 11 to a suite. And they may tie up their gloves while they watch their mates grit their teeth, punch the toilet-stall walls and take their stitches without a whimper. None of them wears tassles.

But when the bell rings Saturday, nobody in these PanAm Game finals wants to look up from his stool and see "USA" coming at him from across the ring.

In the pits of TrujilloAlto, where the refs look the other way and the crowds beg for cruelty, boxing is neither sweet, nor a science. It is like life in the barrios outside - had and earthy, a place only for survivors.

Luckily, the American team brought along plenty of those. CAPTION: Picture, Michael Brooks of the United States jams a two-pointer as Ruben Ridriguez, left, and Carolos Bermudez of the Puerto Rican team watch. U.S. men won, 113-94, to win Pan Am gold medal. UPI