The National Conference of Catholic Bishops yesterday adopted a new guidebook for teaching the faith that includes warnings against such "social sins" as racism, sexism and economic oppression, and acknowledges that salvation is possible outside the Catholic Church.

The 254-page guidebook, called the National Catechetical Directory, was adopted at the closing session of the bishops' four-day conference here. The only comparable effort in American bishops was the 1884 Baltimore Catechism, which has been largely abandoned.

In addition to setting in the basic tenets of the Christian faith as Catholics understand it today, the new Catechetical Directory draws on the social sciences to examine the nature of the contemporary world in which that faith is to be proclaimed.

The new work differs sharply from the old Baltimore Catectism, which arranged the basics of Catholic belief into terse question and answer format which children were required to learn:

"Q: Who made you?

"A: God made me.

"Q: Why did God make yo?

A: God made me to know him and to love him and to serve him in this world and to be happy with him in the next."

In contrast, Archbishop John F. Whealon of Hartford, who chaired the bishop's committee for the new guidelines, said the new directory should be looked upon as setting up parameters" for religious instruction. "It leaves a lot of room for creativity," he said.

It is anticipated that independent Catholic publishers will now develop educational materials for the men, women and children in the pew, within the directory's guidelines. The directory is designed for priests, religious educators and others with some theological sophistication rather than for the average church member.

Bishops in the Catholic Church are traditionally the arbiters of the faith. But in the Catechetical Directory, Archbishop Whealon explained, "We see the bishop as pastor and teacher and avoid the policeman image."

The new directory differs from the understanding of the faith reflected in the old Baltimore Catechism in a number of ways.

Most obvious is the contemporary idea that education in the faith is a lifelong process of spiritual growth which cannot be capsulized into maxims learned by role at age 7 or 8. One section of the directory examines the stages of human growth from birth to "later adulthood" and traces both the aptitudes and the problems for religious growth typically present at each stage.

An entire chapter devoted to religious education for "social ministry" stresses the obligation of all Catholics to attack "social sin".

"Action on behalf of justic is a significant criterion on the church's fidelity to its mission," the directory states. "It is not optional, nor is it the work of only a few in the church. It is something to which all Christians are called according to their vocations, talents and situations in life."

The directory adds that "because social and economic questions are generally decided in the political order, Catholics should play a responsible role in politics, including fulfulling the duties of informed citizenship and seeking public office."

A section on relations with other faiths encourages Catholics to foster ecumenism by presenting "information about other Christians honestly and accurately, avoiding words, judgments and actions which misrepresent their beliefs and practices," while at the same time being open and candid in explaining Catholic doctrine.

Catholics are admonished to "be especially sensitive to relationships with Jewish people" with whom Catholics "share a common heritage," the directory says. It calls for "specific and direct repudiation of anti-Semitism in any form." Catholics and Jews are encouraged to work together in projects and in promoting "a mutual understanding of the Christian and Jewish traditions."

The directory makes no mention of efforts to convert Jews. In a press conference discussion of the direcrory, Bishop William E. McManus of Fort Wayne-South Bend said, "The Catechetical Directory doesn't teach that a person will not be saved if he is not a member of the Catholic Church."