A team of gamblers executed a spectacularly successful betting coup at Pimlico yesterday that produced some crazy payoffs at the track and stunned legal bookmakers throughout Nevada.

As the results came into the betting establishments, "every bookmaker in the state had his heart in his mouth," said Chick DiRocco, editor of the Las Vegas newspaper Sports Form. Not only did the unknown gamblers bet three straight winners, but they inflated the prices on them with an old tactic known as a "builder play."

Nevada race books pay track odds, and these odds can be easily manipulated at a track where there is relatively little money in the betting pools--such as Pimlico on a quiet Thursday. By betting large sums to show on a horse who figured to run out of the money, gamblers could inflate the show payoff on a logical favorite. And that is what they did in two instances yesterday.

In the morning, various customers at Nevada race books were making across-the-board wagers on Dancing Cary in the fifth race at Pimlico, Dear Commander in the sixth and Apparently in the ninth. They were betting as little as $10 to win, $10 to place and $50 to show, and as much as $50, $50 and $500, in addition to win, place and show parlays involving the same horses.

Nevada bookmakers have learned to be wary of such bets--especially if they come from strangers--because of the possibility of a builder play. But the people making the bets today were locals who were acting for the gamblers in the coup. Morever, they were savvy locals. "They knew just the clerks to pick on," DiRocco said. "They were like the card counters in blackjack who know what dealers they can beat."

Today's coup was perfectly legal and ethical. The gamblers were betting on logical favorites, and taking considerable risks. A similar attempted builder play went awry at Pimlico on May 11, when gamblers attempted to inflate the show price on an odds-on favorite, Naughty Jimmy, but lost everything when he finished out of the money.

"Somebody's always looking for an edge," said Pimlico General Manager Chick Lang, who acknowledged that Las Vegas and other Nevada bookies had been hit hard in the past. "This is legal, though rarely done."

In the fifth race at Pimlico today, where the first-time starter Dancing Cary was the 6-to-5 favorite, a bettor went to a window on the upper floor of the clubhouse and wagered $7,500 to show on longshot Buck Bland. When Dancing Cary won easily, he paid $4.60, $3.20 and $4.80, producing the high show payoff because Buck Bland was out of the money.

In the sixth race, the same bettor (with two associates close by) went to the same window and bet $28,000 to show on Tribal Ceremony. When that longshot finished out of the money and Dear Commander won, he paid $3.20, $2.20 and $5 across the board.

For some reason, the gamblers did not make any show bets at Pimlico on the ninth race, but were content to watch Apparently win and pay a normal $5.60, $4 and $2.60 across the board. They won all their bets and all their parlays, amply compensating them for the $35,500 they lost at the track. The precise amount will never be known. "We can't get accurate figures," DiRocco said. "Nobody wants to look like a dummy, and so if you ask a bookmaker how much he lost, he'll say, 'They didn't get me.' "

The nature of today's coup suggests that racing insiders were involved, to some extent. The gamblers made their play in the fifth race on a first-time starter, Dancing Cary, while banking on the assumption that another first-time starter, Buck Bland, would be out of the money.

An ordinary handicapper studying the Racing Form past performances could never have made that play. The gamblers who executed this coup were very knowledgeable and very smart--which is what anybody must be to outfox all the bookmakers in Las Vegas.