WASHINGTON--Robert H. Bork, winding up a record five days of Senate testimony in his struggle to become a Supreme Court justice, said Saturday he will "give everybody a fair shake" if confirmed.

The extraordinary weekend session of the Senate Judiciary Committee was called in part to allow extensive questioning by Sen. Arlen Specter (R-Pa.), who said he was still undecided about the nomination but demonstrated skepticism about Bork's views.

Specter said Bork apparently would vote on the high court against Congress in its bid to restrain presidential war-making powers.

"We have reason to think you're against us," Specter said. "Why should we confirm someone who is likely to rule against us?"

"The impression I always sided with the President is wrong," Bork said. "My record is not one of unvarying support for the executive branch. I will give you a fair shake. I will give everybody a fair shake."

Bork, asked why he wanted to be on the high court, said it would be "an intellectual feast" and added that he would like to leave his mark on the law.

"I would like to leave a reputation as a judge who understood constitutional governance and contributed his bit to maintaining it," he said.

Committee chairman Joseph R. Biden (D-Del.), who previously stated his opposition to Bork, wrapped up Saturday's 34-hour session with praise for the nominee as "an honorable man." Biden said, "I find you neither a racist nor insensitive."

Biden also defended his committee against accusations that the hearings have been mere partisan politics. "I hope you feel this has not been only about politics," he told Bork. "It also is about principle."

Sens. Orrin Hatch (R-Utah), and Alan Simpson (R-Wyo.), lavished praise on Bork and said he emerged from the hearings with more honor than his critics.

Hatch and Simpson both predicted that "never again" would a Supreme Court nominee testify so extensively about his views and professional record.

Meanwhile, President Reagan used his weekly radio address to urge support of Bork. Reagan said there has been "a lot of talk to the effect that Judge Bork was some kind of political ideologue. In truth, Judge Bork's philosophy is neither conservative nor liberal."

The sharply divided Senate committee, after completing its questioning of Bork, plans to turn to other witnesses today who will speak for and against the nominee.

No other candidate for the Supreme Court has testified as long as Bork since the committee began such hearings 48 years ago.

Specter, whose decision on Bork might influence other senators who have not sat through the arduous give-and-take of this week's hearings, expressed concern over Bork's shifting views.

"You have made significant shifts which, candidly, I think have to be evaluated," Specter said. "Your testimony in this room is materially different than what you have written" over the years as a law school professor and later a federal appeals court judge.