Soviet leader Mikhail Gorbachev's opening speech yesterday to the Communist Party congress gave a plug to those pushing for greater economic decentralization but provided few specifics on the pace and scope of the planned changes.

Nor do the proposals Gorbachev advanced amount to a major overhaul of the Soviet Union's state-owned and planned economy. He insisted there would be no "retreat from the principles of planned guidance, but only a change in its methods."

Still, Gorbachev has emerged as the champion of a series of economic reform measures, and here, where economic conservatism has been hemmed in by ideology so long, Gorbachev's ideas mark a break with the past. At the least, they show that the new Kremlin leadership is serious about taking the initiative in the economic sphere, some western diplomats said.

"It may not be much, but in the Soviet context these are the most innovative ideas expressed by a leader since the 1960s," said one western diplomat. "Some of them have been around for a long time, but mostly buried in academic journals."

In the course of his five-hour speech yesterday to the 27th party congress, Gorbachev even called for "a radical reform" of the Soviet economic management system.

In particular, Gorbachev gave his blessing to:

*Increased autonomy for farm and plant managers who will be allowed to dispense anything produced above target levels as they see fit: to sell to one another, to the public or to the state.

*A strengthening of the banking and credit system, considered essential if factories are to become truly self-financed.

*A review of the retail price system, with an eye toward reflecting "the degree to which products meet the needs of society and consumer demand."

*Tying factory payrolls directly to returns from the sale of products, as a way of improving the quality of goods.

He mentioned a large number of other areas in need of improvement, from better statistics to a more efficient use of labor and resources. Gorbachev's main economic strategy has been to accelerate broadening of the nation's technological base, with a major shift in investment to finance the retooling of antiquated factories.

In his speech, Gorbachev also emphasized, as he has done before, a strengthening of the "role of the center" in setting national ecoonmic goals while at the same time warning against excessive "interference" by central planners.

If there are contradictions in the approach, said one western diplomat, "it is because in the end, it is a Marxist doctor giving a Marxist patient Marxist medicine."

Gorbachev's efforts to unleash initiative at the lower levels apparently have clashed with the more conservative thinking still prevalent here.

Today, at a press conference, a deputy chairman of the State Planning Committee, or Gosplan, made a point of playing down any changes, ruling out the possibility of plant closings as a result of efficiency drives and of any expansion of the practice of family farming.

Some observers saw the cautious line taken by the planning officials as a sign that, in some areas, Gorbachev is ahead of the bureaucracy.

In the period before the congress, the Soviet media carried a running debate on a range of sensitive economic issues, from proposals to legalize private taxi services to the morality of people in a socialist society earning extra income.

Both western and Soviet experts concluded that the debate in the press was only the tip of the iceberg and that below the surface, the same discussions were going on in academic and government circles.

The reform group has consisted mainly of academics, many originally from the Novosibirsk branch of the Academy of Scienes, but they have allies in the press and in government.

When the director of the major "self-financing" experiment at a machine factory in the Ukraine was made a government minister last month, the so-called reformists took heart. Another positive sign came on the eve of the congress, when the editor of a newspaper that has carried much of the economic debate was appointed chairman of the state book publishing committee.

The group is well enough established for the economic editor of one influential journal here to refer to it as "our team."

"They [the reformists] are lobbying for their ideas," said one western diplomat. "That doesn't mean they will win, but they are in there fighting."

Already, several commissions studying economic reform have been named within the government. According to one western diplomat, one is studying legal and other obstacles to a limited expansion of private enterprise in the service sphere.

Some of the participants in the debate were on the fringes of public policy only a few years ago. Among those who have achieved new prominence are Abel Abanbegyan, who heads the Institute on Production Forces and National Resources; Tatyana Zaslavskaya, a sociologist from Novosibirsk whose critique of the Soviet economic structure caused a stir several years ago and whose work is now published regularly in popular newspapers, and N. Ambartsumov, an economist now writing in the government newspaper Izvestia who two years ago was chastised for favorable comments on the New Economic Policy, the 1920s policy allowing limited private ownership.

Even television, the most conservative Soviet medium because of its broad audience, has joined in the discussion with a new type of consumer reporting, featuring outraged customers trying to get service at state repair shops.