'Phar Lap' is a winner!

It's unusual to find a good movie about a racehorse. The formulas for this kind of picture are so ingrained that scenes and shots seem programmed in advance. ''The Black Stallion'' jumped this hurdle with a bold mix of intuitive performances and allusive editing. But every other horse opera in recent memory has been a loser.

So it's nice to see ''Phar Lap'' come breezing down the homestretch. It's not a very ambitious movie, even if it is the most expensive Australian production to date. But it tells its story crisply, and it doesn't hesitate to exlore the seamy side - i.e., the money side - of the racing game, along with the usual stuff about galloping to glory.

Phar Lap, a chestnut horse with amazing talent, really lived in Australia during the late '20s and early '30s. According to the movie, he was born ugly and unpromising, taken in hand by a determined trainer, and carefully molded into a winner.

Too much of a winner, in fact. His victories were so consistent that bookies couldn't accommodate them, and threats were made on his life. Meanwhile, the racing authorities - spurred by snobbism and envy, the movie charges - tried to quash him with malicious weight handicaps. Someone tried to kill Phar Lap in 1930 just before a major race. He died suddenly in 1932, at the height of his popularity and success, under mysterious and suspicious circumstances.

The movie focuses on three men connected with Phar Lap's career. The most complex is Harry Telford, the trainer who develops him. His commitment is admirable, but his methods are dubious: He works Phar Lap to a point where an ordinary animal probably wouldn't survive, exploiting the horse's talents to finance an ill-considered ranching operation. The film sees him not as a bad man but as a driven personality with huge blind spots.

More sympathetic is Tommy Woodcock, the stableboy who becomes Phar Lap's everyday handler and best friend. The third man in Phar Lap's life is his owner, Dave Davis, whose concern for racing is closely tied to personal profit and prestige. He's closer than Telford to being a villain, though David Williamson's screenplay shows the better sides of his nature as well as the nasty angles.

All these characters are convincingly played - Telford by Martin Vaughan, young Woodcock by Tom Burlinson, crusty Davis by American actor Ron Leibman. Supporting them are Williamson's well-written script, which avoids most racing-movie cliches, and a wealth of period details (the production was designed by Laurence Eastwood) that catch the moods and trappings of the early depression years. The cinematography is by Russell Boyd, whose exquisite work has graced such films as ''Gallipoli'' and ''Tender Mercies.''

It's ironic that ''Phar Lap'' was directed by a man who has hardly ever set foot near a race track, though this may account for the movie's skeptical view of the racing scene. ''Racing is what we Australians call a mug's game, a devious business,'' filmmaker Simon Wincer told me during a recent New York visit. ''It's too easy to manipulate things, to affect the outcome.''

On the other hand, Wincer has fancied horses for years. This helps explain the film's clear affection for its title character, who's played by a good-looking mount called Towering Inferno - a good name for a movie star!

Wincer is best known to Americans as producer of ''The Man From Snowy River, '' a Kirk Douglas western that has become the most successful Australian film ever. An experienced TV and stage director, he showed some spunk in taking on the Phar Lap story, since the horse still has a near-legendary reputation in his country. Moreover, the filmmaker says, his career is fondly remembered by those who were on hand to witness it.

Was the astonishing Phar Lap supremely talented - or, since he went beyond normal limits, was he a kind of freak? In the film, he's contemptuously called a freak by authorities who see their vested interests dashed by his phenomenal success. And they may be onto something, says Wincer, pointing out that the horse's physical endowments (examined at autopsy) were indeed found to be far greater than those of most horses.

But, the filmmaker quickly adds, this does nothing to diminish the spirit that put those endowments to work, and earned Phar Lap the affection of animal-lovers around the world.