"High Road to China" suggests "Raiders of the Lost Ark" slowed to a crawl. Despite its obvious inadequacies as a sputtering, poky variation on the "Raiders" formula it is nevertheless expected to open big, big at theaters across the country this weekend, owing to Tom Selleck's ineffable hold on a TV public as the debonair sleuth "Magnum, P.I."

Although it moves with the dispatch of a slow boat to China, "High Road" refers to an aerial route intended to be at once scenically expansive and thrill-packed.

This route transports the heroine, Bess Armstrong as a brash American heiress named Eve Tozer, from Istanbul to Sinkiang Province, circa 1920. She is searching for her father Bradley (Wilford Brimley), a missing inventor whose unscrupulous business partner Bentik (Robert Morley, so marginal to the action that his brief appearances always seem awkwardly inserted) has threatened to declare him legally dead within a matter of days (12 is the arbitrary number cited).

The means of transportation are a pair of Stampe biplanes, serviced by a cheerful chubby mechanic nicknamed Struts (Jack Weston) and owned by a supposedly dissipated hero, Pat O'Malley, a hard-drinking World War I ace played by Selleck. Selleck is playfully deglamorized for this assignment by a persistent scowl, a permanent stubble of whiskers and a general disinclination to appear handsomely ingratiating.

Obviously, this grubby, forbidding veneer is meant to age and toughen up an image that ordinarily projects something a bit too passive and picturesquely well-groomed--the essence of a male model, though likably purged of the usual offensive narcissism in Selleck's case.

The filmmakers, and Selleck himself, are smart to want to muss up that excessively smooth TV image on the big screen, but the desired affinities with Humphrey Bogart looking scroungy in "The African Queen" or Harrison Ford looking scroungy in "Raiders" don't quite take with Selleck, who seems like nothing so much as the second coming of Rock Hudson. This isn't totally unattractive, of course, since there was always an agreeable side to Hudson's abiding identity as a Big Handsome Stiff, but the drawback is a similar lack of expressive potency and wit as a leading man.

Watching "High Road," you may begin to appreciate how lucky Steven Spielberg and George Lucas were when they couldn't land Selleck, their first choice as Indiana Jones, oddly enough, and had to "settle for" Harrison Ford. There's a brilliantly camera-wise, inventive, deadpan humorist in Ford, and his reactions added a funny, indispensable emotional validity--a kind of here-we-go-again combination of surprise and vexation with instant resignation and resourcefulness--to the far-fetched perils that Indiana Jones kept confronting and escaping. Selleck isn't a bad actor, exactly, but he still functions like a big, expressively neutral prop in much of "High Road." There are certain simple, winning little acting moments that he can't seem to put across--for example, a hearty drunken belch comes out rather faintly, and the art of holding a leading lady appears to catch him awkwardly unprepared. Apart from his height, there's nothing really commanding about Selleck's presence.

Selleck may be too passive and detached to embody a spirit of high adventure in the elevated, energized comic-heroic style. On a talk show David Steinberg once referred to Selleck and his imitators as "male bimbos," and I'm afraid the term still sticks, even though this starring vehicle is anxious to make it obsolete as far as Selleck is concerned.

The search obliges Eve and O'Malley to bicker their way into each other's affections while hopping from Turkey to Afghanistan to Nepal to China, threatened in the air and on the ground by the villain's hirelings or assorted rambunctious tribesmen. Between threats the exposition dozes off. Those vintage biplanes provide the movie with its only pictorial excitement in the form of redundant but effective aerial stunt sequences, but they also make it ironically impossible to hash out the romance on the wing.

Since Eve and O'Malley can't communicate when they're literally flying from one destination to the next, the movie needs to come to a stop in order to accommodate their little lovers' spats, which aren't written in a particularly edifying or amusing manner anyway but are oppressively prolonged.

A prickly chemistry is supposed to emerge from the intimacy that circumstances force upon Eve and O'Malley, but you're mainly conscious of the strain placed on the actors by all the forced, facetious, near-infantile hostility they're compelled to renew each time the planes need refueling. The curious thing about Armstrong and Selleck as a costarring mismatch here is that they suggest a possibly ideal, humorously appropriate match for another movie that desperately needed rationalized casting--"Victor, Victoria." They're certainly the right ages to play the characters that Julie Andrews and James Garner were a generation too old for, and they might have been the right types, too.

Armstrong bears a strong facial resemblance to Andrews and appears to have a sense of mischief. At the start of her career, she might have been less inclined to take a dignified, ladylike approach to a basically outrageous role. According to a surely preposterous Hollywood rumor, Selleck was originally considered for the title role in "Victor, Victoria." What does make sense is the idea of Selleck in the Garner role; in fact, Selleck's best bet as a star would seem to be the cultivation of an easygoing personality similar to Garner's.

During one of the stopovers along the high road, an Oriental holy man turns up to scatter chestnuts like "The oxen are slow, but the earth is patient." Unfortunately, the pace of the movie is so slack that it's difficult to suppress the thought that while oxen may be slow, they can't be significantly slower than "High Road to China." Fortunately for everyone associated with this incorrigible but harmless klunker, a patient mass audience may be waiting.