Karen Lynn Gorney, the dark-eyed disco dancer who drives John Travolta out of his mind in "Saturday Night Fever", is a new face to moviegoers. But to the millions of fans out there in daytime soap opera land, she is the original Tara, the tragic victim who was torn between two men on ABC's "All My Children".

After winning the strenuous part of Stephanie, Miss Gorney went to work polishing her dance skills with JoJo Smith of the Dance Factory, at Broadway and 54th Street. "He's a fabulous teacher and trainer,"she said. "I practiced for about two months and I kept practicing even after they began shooting the film. I worked on my solos and took classes."

In "Saturday Night Fever", Miss Gorney has a thick, authentic-sounding Brooklyn accent that sounds as though she has spent all her life in Bay Ridge. "I studied drama at Carnegie Tech," she said, "and they taught us how to write down accents phonetically. So I did that with Stephanie's lines - I wrote down the vowel sounds and the consonants. And I hung out with some kids from Brooklyn and broke down their sounds methodically. Some of them were the girlfriends of my co-star on "All My Children", Nick Benedict. They taught me some of the hustle dances they do in Brooklyn, and we'd dance and talk, and I'd write down the way they sounded."

Miss Gorney said she was also inspired by an Italian-American secretary from Brooklyn whom she met in Los Angeles. Ï did a life study of her," she said. "Then I imitated the way she used her hands and her eyes, and the way she chewed gum."

During the filming, Miss Gorney, who is 5 feet 4 inches tall and weighs 103 pounds, said she tried to give added dimension to her character. "I tried to make her understandable," she said. "At the beginning, she was very depressed because she had been deserted by a married man. That's why she was so bitchy to John. I tried to show her as a woman who was really wiped out at the beginning of the film, to one who is finally coming together. Her hair starts to look better in every scene, and I lost 10 to 15 pounds during the filming so I could show her going from a peasant to someone having a sense of how to dress and take care of herself."