Scaly tongue abscesses have to pop in a gore-hound movie like Grindhouse. Key is the detail with which the goopy raspberry-jam eruption dribbles down a doctor’s face into his thick mustache.

Even blood squibs have comic timing in Robert Rodriguez and Quentin Tarantino’s double-feature homage to violent, sexual and cheaply made exploitation films of the late 1960s and ’70s.

It’s largely comprised of two full-length titles — Rodriguez’s absurdly entertaining zombie-apocalypse romp Planet Terror and Tarantino’s talkative, time-taking hot-rod homicide thriller Death Proof. Thrown in are four fake-film trailers thrown together by Rodriguez (Machete), Rob Zombie (Werewolf Women of the SS), Edgar Wright (Don’t) and Eli Roth (Thanksgiving).

With so much stuff (including fake ads for grotesque-looking Mexican food), Grindhouse runs three-hours-plus. It’s just a timed challenge for these directors to remove, impale, explode or gorily drip to the floor every body part possible. (Yes, even the reproductive organs.) Because it’s more “Oh no, they didn’t!” than “Dear God, why?,” the end result is more exhilaration than exhaustion.

After all, as gratuitous as titles got at a grindhouse (theaters so named for former use as burlesque palaces), they rarely set out to seriously offend or disturb. Zombie, Roth and Tarantino all have been involved in movies more thoroughly unpleasant in half the running time.

Here, everyone’s concerned with sufficiently bringing it to have fun with a form. This manic mash-up of 1970s style and modern-day sizzle is a blast, even if Tarantino eviscerates too much momentum at the halfway mark.

Rodriguez clearly loves the stinging-sweet scent of gas in his nostrils, and he rips through the first half in a rush. Spoons could fit in Danny Trejo’s pockmarks, and his weathered mug fills the screen in a coming-attractions spot for the revenge-thriller Machete. (It’s not such a “fake” trailer, as it’s in pre-production for a straight-to-video release.)

Planet Terror slams onto the screen with an instantly fierce competition. Which will shake and shimmy more impressively, Rose McGowan’s go-go dancer or the film’s print itself? Call it a draw.

Intentional scuffs, scratches, discolorations and missing reels all are funky presentation twitches that work. But McGowan’s feral sensuality and sense of humor leads to the best wink-wink gag.

It’s in a superfluous sex scene sandwiched between a laundry list of insane plot points. Government conspiracies, hospital melodrama, bisexual betrayal, trash-talking babysitter twins, barbecue recipes and ogling-camera proof that singer/co-star Fergie still is working on her fitness.

An unleashed toxic gas turns most who inhale it into breathing bubbles of pus with cannibalistic tendencies. When hospitals, police stations and backwoods barbecue joints are overrun, it’s up to a motley crew of survivors (McGowan, Marley Shelton, Freddy Rodriguez, Jeff Fahey, Michael Biehn and Naveen Andrews of Lost) to save their hides and stop a worldwide epidemic.

Unlike Fahey’s prized secret smokehouse recipe, Planet Terror chooses flash cooking over slow roasting. Josh Brolin is brilliantly demented as a devilish doctor with a psychotic taste for revenge, while Fahey and Biehn (as brothers at odds) trade shots with good-ole-boy attitude.

There’s much to cheer in Planet Terror — purposefully garish overacting, blood splattering as if tossed from a shaken paint can, random explosions, a brutally unsympathetic pecking order. It makes sense only on a minute-to-minute basis, but that’s part of the fun that never flags.

Don’t take a bathroom break afterward, as you won’t want to miss any gap-bridging trailers. Zombie’s segment resembles Cabaret crossed with a creature feature and offers a laugh-out-loud cameo. Wright (Shaun of the Dead) sharply sends up how people behave in haunted houses with Don’t. And Roth proves himself the nastiest mind of the bunch with Thanksgiving. It goes well beyond its obvious Halloween reference with depraved catchphrases and slasher-film scenarios.

If the toilet still calls, one could regrettably step out at the start of Tarantino’s Death Proof. And refill sodas and popcorn to finish off in the lobby before coming back.

It tries to be cerebral and a gearhead’s delight all at once. That means there are miles to go before a superior car-chase conclusion, wading through Robert Frost quotations and another overbearing journey through Tarantino’s mental pop-culture catalogue.

Plus, next to Rodriguez’s convulsive presentation, Tarantino seems to find his film to pretty to mark up, although a missing reel throws cold water on planned titillation.

A good movie hides within Tarantino’s not-so-subliminal suggestions for Netflix queues. (Vanishing Point, Dirty Mary, Crazy Larry. Yep, we caught them the first time.) An oily Kurt Russell plays Stuntman Mike, an aging stud of Hollywood’s vehicular-trick scene. His hair seems styled with grease from nachos we see him shoveling down at first glance. His face is like leather tanned for too long. Russell rolls as a dastardly degenerate who, at heart, is a sniveling weenie.

“I’m no stalker, but that doesn’t mean I’m not a wolf,” he tells reefer-scoring young ladies he meets at a Texas roadhouse. Had the movie opened with this, it would be fine. Instead, we get a long, laborious lull of cars-and-bars chatter (not to mention flashes of Tarantino’s foot fetish) between these ladies, who will become his victims. Tarantino’s title comes from how Stuntman Mike has fitted his muscle car to withstand hellacious wrecks, but only for the person driving.

Stuntman Mike reclaims his faded glory by murdering youthful beauty, and the movie gets rolling when Tarantino kicks this character’s impotency undertones into overdrive. Eventually, he’ll target the wrong flock (which includes Rosario Dawson), and Death Proof is flawless once it becomes all fishtails, doughnuts and traded paint jobs on the interstate.

Grindhouse can be a butt-shifter, but it’s electric with a giddy and ghastly charge of having snuck into a cool, restricted-content title after paying for something far tamer.