A federal judge's appointment of a "special master" for Lorton Reformatory's Central facility was delayed yesterday for at least six months after D.C. Mayor Marion Barry named a retired city judge as his special assistant to oversee compliance with court orders affecting the city's prisons.

The unexpected delay by U.S. District Judge June L. Green, who had said only a "miracle" would stop her from naming her own independent specialist to monitor Central's operation, came as the D.C. Corrections Department again delayed prisoners arriving at D.C. Jail from Superior Court from entering the compound, apparently to avoid exceeding a court-ordered inmate population ceiling.

Under the agreement reached yesterday, retired Superior Court Judge John D. Fauntleroy becomes Barry's new assistant, in charge of compliance with court orders that cover the D.C. Jail, Central and two other Lorton facilities.

Green's decision to stay her order for a special master allows Barry to avoid the election-year embarrassment of having the court take direct control of a key institution in the city's troubled prison system. The respite extends well past the Sept. 9 Democratic mayoral primary election and almost to the Nov. 4 general election.

"This appointment is another example of the city getting ahead of the curve and doing rather than having to undo," Barry said in a statement released by his office.

Peter J. Nickles, an attorney for inmates at Central, said he believed Barry's personal commitment to correct problems at the four institutions and the personal integrity of Fauntleroy would yield better and quicker results than a court-appointed master.

Under a new compliance plan detailed to the court, Fauntleroy will have "unlimited access" to the mayor, D.C. officials, Green and inmates' attorneys, and the city must hire a corrections expert to work as a consultant with Fauntleroy.

Green said the consultant must be hired next week from a list of candidates submitted by Nickles and approved by her. The list of candidates was not made public.

Nickles said the arrangement under which Fauntleroy will be "assisted by an expert in corrections" is the "best of all possible worlds, if it works."

He said that Fauntleroy, who is to begin work Monday at an annual salary of $61,978, and the consultant will have access to all departmental records, the same as a special master, but that they will work within the system rather than trying to force change from the outside.

"It is potentially a hell of a lot more effective," said Nickles, pointing out that under the new arrangement Barry's "nose is to the grindstone" to produce improvements.

"Judge Fauntleroy was an outstanding jurist who has a history of fairness and the highest of integrity, which is a reflection of my personal commitment to maintaining high standards of integrity in District government," Barry said in the statement.

City Administrator Thomas Downs said, "This is not a master. It is to reinforce across the government the mayor's commitment to maintaining our compliance with court decrees at the highest level of the government."

Downs said Fauntleroy also will be empowered to make policy recommendations "as it is necessary to stay in conformance with the court mandates in our various institutions."

Green had ordered the appointment of a special master after finding the city in contempt of court, in part for failing to meet deadlines for renovating cellblocks at Central. A contempt of court action is pending before U.S. District Judge William B. Bryant in the D.C. Jail case, in which inmates' attorneys have asked for a $50,000 fine against the city.

Fauntleroy, 65, retired from Superior Court in 1983 after serving 12 years there and three years as a Juvenile Court judge. A native Washingtonian, Fauntleroy served as an active retired judge until last October.

He has had at least a passing involvement in the suit before Green. In 1980 he blocked efforts by the District to help trim its budget by laying off 121 corrections officer at Lorton. Green earlier had blocked the city's efforts to lay off some of the same guards, but her ruling was stayed by the Court of Appeals.

Meanwhile, court and law enforcement officials said more than a dozen prisoners were kept waiting outside the jail for more than an hour Thursday night, even after U.S. marshals delayed transporting them to the Southeast Washington facility for more than two hours to allow jail officials to make room for the prisoners.

Hallem H. Williams Jr., deputy corrections director, denied that the prisoners were kept outside for fear of violating the cap of 1,694 inmates. "There was queueing in the processing area and that caused the delay," Williams said.