Grind (1988)

After three years in a marriage where the missionary position is the dominant position and the cock sucking is out of the questions, Mike Horner, seeks to liberate his sexually inhibited wife, Shanna McCullough. He takes her to a live sex show where she becomes the target of a sex crazed blonde who scares her out of the building. But just when he thinks all is lost, his wife begins to open up, and when she does, he finds the lurid nympho he has always wanted.