Dr. Murdock Head was convicted yesterday of conspiring to bribe two powerful Democratic congressmen in return for their help in securing government grants and contracts for his Airlie Foundation and an affiliated George Washington University department.

A jury in Alexandria federal court deliberated for five hours before finding Head, 57, guilty of conspiring to funnel $49,000 in cash to former Reps. Daniel Flood and Otto Passman, both former House committe chairmen, in exchange for their influence on behalf of his Warrenton, Va., foundation.

It was the second time that Head who holds graduate degrees in medicine, dentistry and law, has been convicted on the charge. His initial three-year prison sentence was overturned by an appeals court this year.

Head also was found guilty yesterday of giving an illegal $1,000 gratuity to Flood in mid-1974 through former Flood aide Stephen B. Elko, whose testimony was agreed by both sides to be crucial to the outcome.

Head, who had appeared self-assured and confident throughout the six-day trial, gave no sign of emotion as the verdict was read. His elder daughter, Kimberly, 28, wept as her father stood facing the jury and she suddenly rushed from the courtroom.

Head's two other children, Karen, 25, and Mark, 27, sat silently among the spectators.

U.S. District Judge Oren R. Lewis, who also presided over Head's first trial, set sentencing for July 17. Head, who faces a maximum seven-year prison term remained free on a personal bond.

Outside the courtroom, Head said he had no comment "under the circumstances" but defense attorney's Frank W. Dunham Jr. and Mark Cummings said an appeal was certain. "We've got an appeal -- I think we've got a good one," said Cummings.

Assistant U.S. Attorney Joseph A. Fisher, a member of the four-man team that prosecuted Head, said only, "We abide by the system."

Both trials were marked not only by publicity surrounding Head and his activities in Washington's circles of power and influence, but by Head's own bitter fight to brand federal prosecutors as vengeful and unfair.

After Head's first conviction was overturned earlier this year, Head issued a two-page statement blasting what he called "rogue prosecutors" who brought "the relentless and punitive machinery of an unbridled judicial bureaucracy" against him.

Head appealed to the Reagan administration to take "a fresh look at the origins of this case, the questionable methods . . . and overall focus and goals of the Department of Justice."

Head said in an interview before yesterday's verdict he had paid more than $100,000 in legal expenses from personal funds, but said he might eventually be forced to seek financial aid from his foundation to continue his defense.

Yesterday's verdict came at 5:55 p.m. after a confused 20 minutes during which the seven-woman, five-man jury at first appeared to misunderstand the charges against Head. Lewis called the jurors into the courtroom and instructed them to vote among themseleves on whether they wished to go home for the night.

Moments later, the panel sent a message to Lewis indicating they had reached a verdict on two or three counts -- an impossibility since Head was charged in a two-count indictment.

Lewis called the jury back to the courtroom, repeated an explanation of the two charges and sent them back into seclusion.

Defense lawyer Dunham stood and began to object, saying "I don't understand . . ."

"I don't want to argue it," shouted Lewis, a crusty, 79-year-old jurist. "You can take the press outside and make a speech."

Dunham then demanded Lewis declare a mistrial, which Lewis refused to do.

Shortly afterward the jury returned to the courtroom with the guilty verdicts.

One juror, John Henry O'Quinn, 36, of Woodbridge, said last night the confusion arose out of the way the indictment was worded. The document listed two counts -- bribery conspiracy and the illegal gratuity -- but also cited three specific acts by Head which the jury had been told to consider in reaching a verdict.

Asked if testimony by Elko, who has been convicted of fraud and perjury in an unrelated case, was important to the deliberations, O'Quinn said, "It was to me. I though Elko had a lot less to lose than Dr. Head."

A second juror, John P. McKinley Jr., 37, of Vienna, said the panel took "less than an hour" to agree on a guilty verdict on tax-evasion aspects of the conspiracy count. "We just realized, here was a man [Head] who said he was giving all these campaign contributions [to Flood], and he had no receipts, no anything," McKinley said.

He said the jury finished considering the conspiracy charge by 3 p.m. and spent the reminder of its deliberations on the illegal-gratuity allegation.

Judge Lewis began yesterday with two hours of jury instructions, citing what he called the "inordinate amount" of disagreement among witnesses in the two-year-old case.

"Basically, Elko and Head just don't agree at all," Lewis said of Elko's allegation that Head had funneled $49,000 in what Elko called "taxi fare" or "grease" to Flood, Passsman and himself.

Lewis ordered the jury to adhere strictly to a five-year statute of limitations dating from July 12, 1974, in considering any so-called "overt acts" that furthered the alleged conspiracy between Head and numerous unindicted coconspirators.

Head's first conspiracy conviction, in October 1979, was overturned by a federal appeals court in Richmond on grounds that Lewis had improperly instructed the jury on the statute of limitations.

Head, in a dark blue suit, sat solemnly in the windowless, second-floor courtroom as Lewis spoke. He stared often at the jury, kneading his palms continuously in a hand-washing motion and appearing to listen intently as the detailed instructions were read.

During the six-day trial, Head took the stand in his own defense to testify that on two or three occasions in the 1970s he had given $300 to $500 to Elko as campaign contributions for Flood. He strongly denied the cash payments were intended as bribes, as Elko and the prosecution contended.

Head also denied any illegal intent in backdating leases of buildings at Airlie, actions that effectively reduced the tax liability of Raven's Hollow, the foundation's filmmaking affiliate, in 1974 and 1975.

Head acknowledged that Raven's Hollow maintained a cash fund of up to about $90,000 -- first in his desk drawer and later in an office safe -- but characterized the money as a contingency fund to cover lost film equipment and for use in the organization's film projects overseas.

Head testified he last saw Elko at Airlie in 1977 after Elko's conviction in California in an unrelated fraud case. "He was pushing me, talking gangster talk," Head said. Head said he refused Elko's demand for $8,000 to help pay his legal expenses, and that shortly afterward Elko began making his allegations about Head to federal investigators.

In closing arguments on Tuesday, prosecutors scoffed at Head's claims, calling him the "major-domo" of Airlie and contending Head had intimate knowledge of a scheme to generate cash through phony travel vouchers signed by numerous Airlie and Raven's Hollow employes.

Financial records at Airlie were a "hall of mirrors," one prosecutor said, overseen by Head, the "master plotter and master of detail."