In “The Nice Guys,” director Shane Black and producer Joel Silver go back to the ’70s to relive their 1980s glory, those guns, giggles and gore action comedies like “Lethal Weapon” and “The Last Boy Scout.”

A hilarious Ryan Gosling and a gruff and grumpy Russell Crowe are the oddball pair in this “48 Hours” riff, two LA detectives — actually, one’s more an “Equalizer” than PI — thrown together in the search for a supposedly dead porn star.

It’s too long, and the mistaken-identity porn star bit makes only so much sense. There’s a “cute kid” for the guys to shoot, kill and cuss around. And the body count is packed with innocent bystanders.

But hey, it’s LA in the ’70s. It’s all in good fun!

Crowe is Jackson Healey, a guy you hire when you want somebody to stop coming-on to your under-age daughter, or to stop somebody from stalking you. That latter request comes from Amelia (Margaret Qualley), a fetching 20something who wants this guy to stop following her.

Gosling is Holland March, an actual private detective. He’s been hired to find Amelia, but Healey doesn’t know that as he’s breaking his arm. Literally.

March is a single dad, and that sassy, worldwise 13 year-old (Angourie Rice) amply illustrates one of Healey’s narrated gripes about the city.

“Kids today, they know too much.”

Her daddy? Not so much. He’s a lousy private eye. He’s clumsy, he cheats his clients and he’s plainly not tough in that LA detective Sam Spade/Philip Marlowe mold. Sunglasses, a license to carry, a love of booze and cigarettes are just not enough.

“I’m done. Put a fork in me. Don’t…put a fork in me.”

Gosling’s impish side is put on display here, as is his gift for physical comedy. Funniest scene? Him, a toilet, a .38 and a cigarette dropped down his pants. He gives that bit a run for its money several other times in the movie’s two hour run.

Crowe, as he proved when he bombed on “Saturday Night Live” a few weeks back, doesn’t have those gifts. He’s a born, gruff straight-man, 50something, barrel-chested, good at playing a cynic whose divorce made him bitter. How bitter?

“Marriage is buying a house for someone you hate.”

As in co-writer/director Black’s best movie, the film noir detective comedy “Kiss Kiss, Bang Bang”, “Nice Guys” is peppered with wisecracks and “funny,” bloody deaths, like the nude porn starlet who dies in a gruesome car crash in the film’s opening scene. We see people in adjoining apartments or bystanders at a party go down in a hail of bullets.

Hilarious.

The porn industry of the era is as much a part of the movie as the classic cars (re-used in the background, in scene after scene) and the leisure suits.

But the zingers, which fall off markedly in the latter third when the energy flags and the plot unravels, always pack a punch.

The single-dad finds himself around 13 year-olds, some of whom aren’t his daughter. He can’t help but let a profanity fly.

“Jesus top-popping Christ!”

“You took the Lord’s name in vain!”

“No, I didn’t, Janet. I find it very useful.”

Kim Basinger plays a Fed, the great Keith David plays one more heavy and there’s a hit-man with a certain physical resemblance to a popular TV star of the ’70s.

And there’s Crowe, an Oscar winning outcast still trying to win the audience back, never cracking a grin, occasionally letting us see his softer side (he does more of that in “Fathers and Daughters,” opening in July). He should have studied Nick Nolte’s bearishly over-the-top turn in “48 Hours” more closely, because he needed to play this guy bigger, louder, testier.

But his comic shortcomings don’t ruin the movie. They just put restraints on a comedy , a potential franchise, that could have really taken flight. Because we’re rooting for these “Nice Guys” to finish not last, but first.

MPAA Rating:R for violence, sexuality, nudity, language and brief drug use

Cast: Russell Crowe, Ryan Gosling, Kim Basinger, Keith David, Angourie Rice, Margaret Qualley
Credits: Directed by Shane Black, script by Shane Black and Anthony Bagarozzi. A  Warner Brothers release.

Running time: 1:56