During two hours of cross-examination today, businessman W. Dale Hess stuck to his theme that he was "not trying to hide anything from anybody" when he altered records about financial payments he made to Maryland Gov. Marvin Mandel and back-dated a document to explain them as repayment of a debt to Mandel.

Hess testified that he took these actions for his own personal record-keeping needs, and not as part of a cover-up, as alleged by federal prosecutors.

Hess grew increasingly angry today as he answered a battery of questions about his major role in both the secret Marlboro Race Track purchase and the business ventures he shared with Mandel.

"What are you trying to get at," Hess demanded of assistant U.S. attorney Ronald Liebman as the prosecutor brought up a major coincidence that he suggested led to a cover-up.

In the month after Hess was officially notified in 1974 that he was under federal investigation, Leibman pointed out, the codefendant altered his records to indicate that the payments were legal fees not income from a real estate deal. He also ordered his secretary to type out a letter, backdated to 1968, stating that he owned Mandel $15,000 in legal fees.

Hess held fast to his basic contention that he did not give Mandel bribes and he did not tell the governor about his secret purchase of the Marlboro Race Truck with codefendants Harry W. Rodgers III, William A. Rodgers, Ernest N. Cory Jr. and, allegedly, Irvin Koens.

Hess said he lied to the governor twice to keep him from knowing of the purchase. Prosecutors contend in their multicount indictment that Mandel knew at the time that his friends purchased the track and purposely lobbied for legislation to bring financial gains to Marlboro.

In return, the prosecutors charge, Mandel received $350,000 worth of gifts and favors from his codefendants including the $15,000 payments from Hess for his share in Security Investment, the real estate venture.

Both Mandel and Hess have testified that for six years ending in 1968 Mandel performed legal services for Hess and never asked for or received any payment.

"It was a gentlemen's agreement," Hess said today, explaining why he signed over to Mandel a 4/9 interest in his $250,000 share of Security Investment, which leases building to the Social Security Administration facility outside Baltimore.

Why did Hess decide to pay off a debt he hadn't even computed by signing a partnership agreement rather than writing out a simple check, Liebman asked.

"Well," Hess answered, "I didn't handle it that way because I decided this was the way I was going to do it."

Prosecutors have contended that the legal fee explanation was an afterthought to avoid fraud charges. When Liebman elicited Hess' explanation for the back-date letter and altered check stubs, he was reprimanded by Hess.

"It was not done to hide anything from anybody," Hess said, leaning forward in his chair and clenching his teeth. He accused Liebman of using the documents to "find some reason to get me here."

"I wanted the records to reflect what really happened." Hess said of the doctored check stubs.

In 1972, Hess explained, he instructed his secretary to make checks to Mandel for 4/9 of his income from the Security Investment Company. When his accountant, who testified for the prosecution earlier in the trial, asked the next year what the payments "M.M. - Sec. Inv." meant, Hess said he explained the payments were for Marvin Mandel's share of the income.

Why didn't you tell your accountant then it was for legal fees?" Liebman asked.

"I don't recall," Hess answered.

One year later, and one month after Hess had been notified he was under investigation, he had another talk with the accountant.

"That time you mentioned legal witn no mention of Security Investment," Liebman reminded Hess.

"Yes, sir . . . that's when Mr. Sachs (the accountant) said this was a legitimate legal expense."

That was also when Hess ordered his secretary to go to the office he used in 1968, type a letter on stationery used in 1968 and on a typewriter used in 1968 and write the note addressed to Mandel confirming that Hess owned him $15,000 for legal today.

"The letter was typed so Mr. Sachs would have something in his file," Hess explained. "It wasn't really a false date (the 1968 year typed in 1974) . . . The date reflects what happened during that period of time."

When Liebman suggested that the letter was typed because Hess was notified he was under investigation. Hess swirled in his chair and looked to his attorney William G. Hundley:

"I knew at least a year earlier," Hess said, "you were asking questions about me in the grand jury. That's when I retained Mr. Hundley. All the lawyers in the Baltimore area were used up," referring to the number representing other people under investigation by Liebman and his colleagues. 0584ADD EIGHT MANDEL - AR

Liebman also asked Hess if he didn't arrange a laundered $42,000 loan through the Catholic Pallottine Fathers for Mandel because he wanted to hide his involvement from the federal investigations.

"That is untrue," Hess said. "Absolutely untrue. I did not involve the Pallottine Fathers, Mr. Webster involved (them). That was a legitimate loan from the Pallottines to the governor."

Last week Mandel testified that he did not know for more than a year that the Pallottine Fathers bankrooled the 1974 loan that he used to make a divorce payment.

"Didn't Donald Webster testify in this very courtroom that you told him you couldn't make the loan yourself because you were under investigation?" Liebman said to Hess.

Liebman also suggested that another business deal cited in the indictment, a real estate venture called Ray's Point on the Eastern Shore, involved a coverup.

"Could you give us an explanation why Marlyn Mandel's name was taken off the corporate minutes of Ray's Point," Liebman asked Hess.

"I don't have any memory at all about the minutes," Hess answered.

The prosecutor, after noting that Mandel's stock in the venture was held under Hess' name, offered an explanation why Mandel's role was secret.

"You and your friends (two other codefendants) didn't want to take any chance of anyone learning Marvin Mandel was in Ray's point because you were pushing the (race track) consolidation bill . . . that very same time, in March, 1972, isn't that true?" Liebman asked.

"Absolutely not," Hess said, explaining that he was lobbying for the bill that would have benefited his secretly owned track but that it had nothing to do with the business venture with Mandel.