Cry Uncle

(1971)

Directed by John G. Avildsen
Written by David Odell from a novel by Michael Brett; Additional dialog by Alvildsen and Garfield.
Starring Alan Garfield, Madelyn Le Roux
IMDB  Entry
When the MPAA rating system when first implemented, some directors decided to make the most of their new freedom with sexual matters.  The X rating was not solely for porn (as it soon became), a handful tried to make good movies that were still more explicit than the R, seeing how far they could push the envelope.  Cry Uncle tore up the envelope and stomped on the pieces.  Even today, it is still probably the raunchiest film put out by a major studio.
Director John G. Avildson made a career to turning actors into stars.  His first major film, Joe, brought Peter Boyle and Susan Sarandon to the attention of the movie-going public. His best-known film is Rocky, which made another unknown actor into a star.  Jack Lemmon, though established, won an Oscar in Avildson's Save the Tiger (seven actors got Oscar nominations for their work in Avildson's films) and The Karate Kid promoted Ralph Macchio and Pat Morita to movie presences. 
Cry Uncle did the same for Alan Garfield.  Admittedly, Garfield (sometimes billed as Alan Goorwitz) never became a star, but he was one of the top character actors in 70s and 80s, and is still working today.  He showed up in dozens of TV shows and movies (including The Conversation, Nashville, The Stunt Man, Cotton Club and Beverly Hills Cop II), a chubby, balding guy, with a whiney voice and thick New York City accent.
When it came out, Cry Uncle was rated X -- one of a handful of legitimate films of the time to get that rating.  Today, of course, it would be an R -- barely.  It reveled in its raunchiness and sex.  Nowadays, there are films like that (e.g., American Pie), but they tend to focus on teenagers, and the issues with getting someone to bed.  They are sex comedies for teens. 
Cry Uncle is a raunchy sex comedy for grownups.  It's set up as a detective film:  Garfield plays Jake Masters, private eye, investigating the murder of a porn actress/hooker.  It takes him into a world of sexual intrigue.
And all the sex is upfront.  The movie is never coy about it:  this is true bawdiness, where the sex is there for all to see.  Though it's portrayed a bit more discretely than porn, the dialog is filled with blatantly blunt talk of sex.
And it's funny.  Part of the joke is that the dumpy Garfield is able to get as much sex as he wants (sometimes more than he wants).  And the scene of the inadvertent necrophilia is priceless.
The film was probably never shown on TV (there was no way to  cut it down and still make sense), and by the time HBO came along, it had been forgotten.  The movie is not for everyone, and the language is going to put a lot of people off.  But if you have the sense of humor that thought American Pie was too tame, this may be worth a shot.