There was a noticeable, sometimes bitter feeling of disappointment among blacks here today that whatever Jimmy Carter has done to anger South African Prime Minister John Vorster, it was not enough.

Frustrated by unanswered questions surrounding the death of black leader Steve Biko and demoralized by the detention last week of most of their most outspoken leaders, the people of this black township on the outskirts of Johannesburg began learning last night that the United States had stopped short of economic sanctions in exerting pressure on the Vorster government.

For many, it was a letdown.

"I was disappointed," said Mamasseh Moerane, whose Association for Educational and Cultural Advancement was banned last week. "But I thought, maybe the Carter administration needs a little more time to consider it."

Then he sighed and asked, "is the U.S. prepared, really, to put the squeeze on South Africa?"

"I see it as a beginning," said a social worker. "After all, of the hundreds of people who have been shot, some of those bullets must have come from America."

A white-collar worker added: "With the insults South Africa has been saying against the States. Carter should have done more than this. An arms embargo is cosmetic. South Africa is already producing 90 per cent of its own arms."

There has long been some support for economic sanctions against South Africa within the black community, but it has often been argued that pulling foreign investment out of the country would hurt the black man more than it would the white.

Five years ago, a team led by Rep. Charles Diggs Jr. (D-Mich.) made a study here and concluded that blacks felt it would be better to work from within the business sector for improvement of their lot.

"It's hardly five years, and that has changed completely," said a businessman who, like most people interviewed since last week's bannings and detentions, asks anonymity.

"The better for the Carter administration to pull out now," he said. "We have suffered for 300 years now, and if tha means we have to suffer for two or three more decades even, it won't matter."

"I am disappointed" said a community leader who saw most of his associates go to jail last week."The trade and commercial enterprises are the topmost priority. They should have been first priority - cut off completely - because as they say, we blacks have got nothing to lose.

"It makes no difference at one stage or another whether we have employment or not. because even with employment, we have nothing."

The feeling that the United States and other Western countries should do their best to wreck the economy here is somewhat akin to a military commander calling in artillery fire on his own position because the enemy is all around him.

More than 350 American companies in South Africa, with a total investment of about $1.6 billion, employ thousands of blacks. Diplomatic observers argue that even by removing that investment the South African economy would not collapse.

But with the increasing frustration following the death of Biko, the black consciousness leader, and the government crackdown last week, there is a growing sense that the only way the black man is ever going to get a piece of the action in South Africa is to pull the whole economy down.

One of the few people willing to go on record in Soweto these days is T. W. Khambule, who has just quit as principal of the township's largest school, Orlando High.

He, too, has seen a change in attitude over economic sanctions, and he favors them.

"It really doesn't help," he said of American investment. "It stabilizes the government. When the economy is good the rulers can enforce their repressive laws."

Khambule presents this paradox: while the whites insist that blacks are unfit to run the economy, the white government stifles the development of a black commercial class.

"They talk of free enterprise," he said. "The black man doesn't know free enterprise. In most cases, he's not allowed to own more than one of those little shops you see around here."

Hours before President Carter's announcement of the expanded arms embargo yesterday, South African Finance Minister Owen Horwood told a luncheon of American businessmen that America needed the South African market, reminding them that the United States exported nearly $1.5 billion worth of goods to South Africa last year.

A Soweto shopkeeper walked around his store today and read off the U.S. brand names.

"Forty per cent of my goods are American," he said. "Take them away and who do you hurt? The African? We can live on mush and water."

Outside a primary school, a group of teachers idled by a student boycott that has now spread all the way down to first grade were asked whether economic sanctions would not hurt the black man more than the white.

"Don't worry," said an aging teacher. "You will just put pressure on a man who is already suffering."

"Cut it, get rid of it, take your business and get out," said a younger man angrily. "What can it do to Soweto? People here have nothing to lose."

The older man spit hard into the dust and frowned.

"What good is my job without my freedom?" heasked. "We are all Steve Biko now. We are ready to die."