Jack Valenti's best-selling "Speak Up with Confidence" is the sixth book he's written on weekends.

From noon to 3 every Sunday, he sits at the typewriter, aiming for 2,000 words. "At the end of a year, if you stay at it, you've written 100,000 words," he says. That's a book and that's a wrap.

In his work as president of the Motion Picture Association of America, the trade association of the film industry, Valenti travels to California three times a month, and he uses some of his time on the plane note-taking for his books. "I don't like to chat around with people I don't know," he says.

Valenti refers to himself as an amateur writer. "It's a lot of fun for me. It's great therapy for me, so I enjoy it. It extracts me from my own pressure-ridden world. I am lost in a new environment that I create."

Two of the books haven't been published: One was a novel he tore up as soon as it was written, and the other is a book on the presidency, which he says is "not quite right yet."

For recreation, Valenti plays combat tennis, usually at 7 or 8 in the morning at St. Alban's. "I play tennis to win. I don't play pattycake tennis.

"If I am playing doubles," said Valenti, "I am concentrating on taking no prisoners."

For more exercise, he jogs a couple of miles a day. "I don't find it rewarding, haven't been hooked on it. I do it for stamina." And he does calisthenics. "When you get as old as I am, you have to do a lot," says the 60-year-old executive.

Valenti, once the top aide to Lyndon Johnson, isn't a frequenter of the so-called Washington party scene. "That's observed more in the imagination than in the reality," he says. "I go to a dinner party about once a week with friends," where guests number between 10 and 20. "I don't go to balls or big affairs. You see somebody's name in the paper once, and you think he must be going out every night of the week."

Valenti's idea of a great time is showing a movie to "a few friends" at the MPAA, in an intimate theater with plush seats and red carpeting. "I really love that, to gather friends around, have a little drink, a bite to eat, then top it off with a first-class movie. Particularly one I have already seen that I really know is going to stir them."

Valenti, the man responsible for the motion-picture rating system, has seen "E.T." four times. He admires Steven Spielberg's movie for its craftsmanship. "An eight-year-old, a 30-year-old, a 50-year-old and an 80-year-old can all enjoy this film at different levels," he says. "There are very few films that can make that statement. It's charming, delightful; it's a fairy story.

"It doesn't have any polemics, doesn't instruct you in anything."

Movies should first entertain, Valenti says, and he feels the same way about books. "My favorite historian is Macaulay because he's never dull -- the great master of the dramatic narrative," says Valenti, who has read everything Macaulay ever wrote.

In his free time, Valenti skims any current novels -- "You can read them in a couple of hours" -- with an eye to keeping up with books that will be made into movies.

By the same token, he has the perfect justification for watching television. He looks out for made-for-TV movies and all the new shows "to know what's going on in my business." He loves "Hill Street Blues" and "M*A*S*H" reruns.

Valenti may dine at a restaurant on the weekend, but usually only if someone he knows is visiting from out of town. He likes Maison Blanche, Le Steak and Jean-Louis at the Watergate, but his first choice is Le Lion d'Or, where he orders fish or veal: "It's sensational -- as good a restaurant as you'll find anywhere in this country."

Other times, he'll take his 13-year-old daughter and 16-year-old son to Roy Rogers. "See America," Valenti says.