"Dead Men Don't Wear Plaid" is a curiously overextended spoof of the cliche's of Hollywood's hard-boiled mystery melodramas of the 1940s. The nonsensical title was coined to kid doomful beauts like "The Postman Always Rings Twice" and "The Damned Don't Cry."

Steve Martin, whose starring performance as the tenacious shamus Rigby Reardon is usually right on the deadpan button, advanced the movie with at least one inspired trailer. The catch is that the trailer was also a more accomplished and satisfying put-on than the finished film, which wears itself out by indulging in a single tongue-in-cheek, movie-conscious jest to tedious excess. The movie uses as a device the insertion of scenes from Hollywood prototypes, intercut in such a way that Martin appears to be confronting, for example, Alan Ladd in "This Gun for Hire" or Cary Grant in "Suspicion," conducting telephone conversations with Barbara Stanwyck in "Sorry, Wrong Number" or Humphrey Bogart in "The Big Sleep" and--the most outrageous juxtaposition of all--"kissing" Fred MacMurray in "Double Indemnity" during a stretch in which Rigby pretends to be a woman.

"Plaid" has been shot in black-and-white and dressed with '40s decor and costumes. In fact, it was the last production which enjoyed the services of the late Edith Head as costume designer, and there's a far more confident, playful sense of period evocation in her clothes and John De Cuir's sets than in the imitative and sometimes desperately cramped pictorial schemes employed by director Carl Reiner and cinematographer Michael Chapman.

Although it runs barely 90 minutes, it begins running down prematurely because the excerpts have been permitted to multiply unwisely and assume a disproportionate importance. "Plaid" incorporates material from 18 old movies, and in some cases borrows several scenes and prolonged excerpts. This is way too much. A half-dozen clips inserted selectively would seem a better proportion. It's self-defeating to leave the impression that you wouldn't have a new movie unless you were scavenging extensively from old movies.

What makes this imbalance even more dismaying is the relative perkiness of the material invented by Martin, Reiner and cowriter George Gipe in affectionate mockery of detective movies. The plot outline seems flexible and suitably preposterous. Rigby is hired by a ravishing but perhaps treacherous lady in distress, Juliet Forrest, to locate her father, an eccentric inventor kidnaped while tinkering with cheese manufacture. Evidently he blundered onto something that could have cataclysmic military applications, and the twisted trail leads Rigby and Juliet to a gang of Nazis.

Envisioned as a sultry '40s temptress, Juliet is lushly embodied and impeccably played by the seductive sensation introduced in "Sharky's Machine," the husky-voiced British beauty Rachel Ward. She and Martin make a funnier pair of smoldering lovers than the movie can take advantage of. It needs more of their breathlessly silly interplay.

I felt mildly misled by one aspect of the presentation. Early publicity releases had led me to believe that Martin would be inserted frequently, by the magic of composite photography, into the vintage clips, but there's only one example of this beguiling form of illusion, previously used in the oddball comedy "The Projectionist" and improved recently in Dick Cavett's time-traveling specials for Home Box Office--Rigby sharing a train compartment with the Cary Grant character in "Suspicion." In every other instance Martin's scenes are intercut, more or less effectively, with the borrowed material. While this form of juxtaposition may pay off--one of the better running gags is the way Rigby keeps scolding Bogart, supposedly a mere operative of Rigby's named Philip Marlowe--I don't think it offers nearly as much to either uninitiated or knowing moviegoers as a perfected form of composite imagery.

Martin's comedy technique seems demonstrably sharper for the experience of "Pennies From Heaven." He's got an exact appreciation of his relationship to the camera that seemed utterly beyond his perception or skills in "The Jerk." It would be a considerable humorous loss if Martin were somehow prevented from applying what he's learned about movie acting, simply because fans prefer the old Steve Martin. It's not as if Rigby Reardon is heavy stuff, after all; it simply proves that Martin's got what it takes to characterize a classier kind of jerk.