The Democratic Party's rule makers, moving rapidly away from the "reforms" of recent years, yesterday rewrote the 1984 delegate-selection procedures in ways likely to increase the power of big-state delegations, elected officials and party leaders.

They also increased the maneuvering room of all delegates and made it more difficult for the adherents of minority causes and candidates to be as influential in convention hall as they were in 1972, 1976 and 1980.

In the future, personal pledges or state laws notwithstanding, delegates can vote for any candidate. The principle of proportional representation that allotted delegates to trailing candidates in primary elections will be bent in states that choose to use bonus delegates or a so-called "loophole" primary.

In a night and day of fast-moving decisions at the Shoreham Hotel, the party's commission on presidential nominations, headed by North Carolina Gov. James B. Hunt Jr., also delayed the start of the 1984 voting by pushing the Iowa caucuses from late January to late February and the New Hampshire primary from late February to early March.

Hunt said at the conclusion of the session that the decisions will "help us win and help us govern. They will make the convention more representative of the mainstream of the party."

In three sessions that began after dinner Thursday and ended yesterday evening, the Hunt commission:

* Set aside about 550 seats at the 1984 Democratic National Convention, about 14 percent of the total, for unpledged elected and party officials, including up to two-thirds of the Democratic U.S. senators and representatives.

* Freed pledged delegates from the threat of replacement by the candidates they originally promised to support and allowed them leeway to reflect the changing sentiment of their constituents.

* Permitted all states to provide a bonus for the winning candidate at the expense of trailing minority candidates.

Permitted Maryland and a dozen other "organization states," including New York, Pennsylvania, Ohio, Illinois and Texas, to return to the previously banned "loophole primary" where a plurality of voters supporting the leading candidate can elect all the convention delegates.

The changes, reversing the trend of the past 12 years toward increasing grass-roots activists' control of Democratic presidential nominations, were supported, in the main, by members of Congress, state party chairmen, leaders of organized labor and representatives of former vice president Walter F. Mondale and Sen. Edward M. Kennedy (D-Mass.).

The dissent, which was only occasionally emotional or spirited, came largely from a handful of feminists and "reformers."

The recommendations will be approved in final form by the commission at another meeting in early February and then must be reviewed by the Democratic National Committee before they go into effect.

Under the new timetable, Iowa retains its status as the first caucus state, but would move its date from Jan. 21 as it was in 1980 to Feb. 27 in 1984. New Hampshire's would still be the first state primary, coming on March 6, 1984, instead of its Feb. 26 date of 1980.

Maine, Massachusetts and Minnesota--the other early-starting states in 1980--would have to apply for exemptions from the general starting date of March 13 for delegate selection, if they wanted, once again, to jump the gun.

What the commission did on the major issues:

* Unpledged delegates: More than 400 slots for unpledged delegates will be apportioned among the states, on the basis of the size of their delegations and the number of major elected Democratic officials. As of now, they would share 437 seats, but the number will fluctuate with the 1982 election returns.

Among those unpledged delegates will be up to two-thirds of U.S. House and Senate Democrats, chosen by their respective caucuses.

The remaining uncommitted slots will be distributed by state committees to Democratic governors, big-city mayors and other elected and party officials. In addition, each state's Democratic chairman and vice chairman will be made unpledged delegates, bringing the total to about 550 in a roughly 3,800-member national convention.

The inclusion of unpledged delegates passed, 47 to 6, after a proviso to require half those seats be reserved for women was defeated, 42 to 14. However, the rule requiring the entire convention to be balanced between men and women was reaffirmed. That will require that there be more women than men among the pledged delegates.

* Pledged delegates: With little controversy, the commission scrapped the so-called "robot delegate" rule that provoked the 1980 fight between backers of President Carter and Kennedy.

The commission unanimously killed the "jerking" rule that allowed a candidate to pull off the convention floor any delegate who threatens to bolt and bring in a loyal replacement. The loyalty-pledge language was also loosened.

In 1980, the rule said all delegates were bound to support, for at least one ballot, the candidate they were elected to support. The new rule says only that they "shall in good conscience reflect the sentiments of those who elected them."

* Proportional representation: The commission voted to allow both caucus and primary states the option of offering a "winner-take-more" bonus of one delegate in each congressional district to the high candidate in that district, before the remaining delegates are apportioned by popular vote.

More important, the commission restored to all states the option of using the so-called "loophole primary," in which individual delegates are elected directly by voters at the congressional district level. In 1976, 13 states, including Maryland and several of the biggest states, used "loophole primaries."

But in 1980, after the rule was changed, only Illinois and West Virginia were allowed such primaries. Many of the others are now expected to restore their "loophole primaries" as a way of increasing their influence in the nominating process.

They are called "loophole primaries" because a presidential candidate whose delegates win pluralities in their contests can get all the delegates in a district without a majority of the votes, despite the general rule of proportional representation.

The changes were made in response to complaints that the 1980 rule of strict proportional representation made it harder to get consensus on the leading candidate, Carter, and sustained the candidacy of his challenger, Kennedy.

But on this issue, as on most of the others, Kennedy's representative, Jack English of New York, voted in agreement with Mondale's spokesman, Washington attorney John Reilly, and the vast majority of commission members went along with them.

The only clear Mondale-Kennedy split came on the timing of the Iowa caucuses, with the Mondale forces backing the state's desire for a Feb. 27 date, and Kennedy's friends joining most union delegates in an unsuccessful effort to delay them until March 5, the eve of the New Hampshire primary.

Mondale, a Minnesotan, is considered the early favorite in Iowa.