A BUNCH OF bumbling would-be arsonists set up an elaborate arrangement of explosive material to destroy the old Adelta Manufacturing plant, in North Philly, in 1974.

They installed 20 55-gallon drums of gasoline in the building, set up an explosive device to destroy the sprinkler system, wrapped hot plates in paper towels to set off the gasoline and installed timers.

"It might have been the scariest thing in my fire-service career," said Capt. Pat McGinley, of the fire marshal's office. "Any spark would have blown that building apart. It would have moved that building from 9th and Dauphin to 10th and Market."

But the conspirators miscalculated. The explosive device in the sprinkler system went off prematurely, and police and firefighters, alerted by the relatively minor damage, discovered the deadly stack of gaoline drums.

What remained was tracking down the perpetrators.

That was the job of William J. Drum, the highly regarded agent of the U.S. Bureau of Alcohol Tobacco Firearms and Explosives.

Using his many sources and informers, Drum soon rounded up a nest of suspects, some of whom went to prison. The owner of Adelta, Robert Corbman, pleaded guilty to hiring the conspirators to torch his building.

Bill received the Treasury Department's Meritorious Service Award for cracking that case.

Bill Drum, an ATF agent from 1960 to his retirement in 1980, former investigator in the Philadelphia District Attorney's Office, a Navy veteran of World War II, a former security officer for Harrah's Casino in Atlantic City and a devoted church deacon, died Wednesday. He was 85 and lived in Blackwood, N.J.. He formerly had lived in Fairmount.

"He had a stable of informants," said James Kelly, retired ATF agent who worked with Bill. "He was the personification of the U.S. Treasury agent. He was a hard-nosed, take-no-prisoners type of guy who never let up on a case. He worked 12-16 hours a day, seven days a week."

But Bill's determination "was tempered by his qualities of kindness and compassion and understanding of the individuals he arrested," Kelly said.

Bill also traveled the country with former Vice President Hubert Humphrey as part of his security detail when Humphrey ran for president in 1968. He had his hands full when the campaign took Humphrey to Chicago, where police famously cracked down violently on anti-war protestors.

Francis Lederer, onetime chief of detectives for the D.A.'s office, where Bill worked before joining the feds, said that Bill was "a decent man and a very efficient investigator. . . . He was honest as the day is long. He was always there, always on the job. He was very good with bench warrants; he was good at tracking down fugitives."

As an ATF agent, Bill locked up organized crime figures, professional killers, outlaw motorcycle-gang members, and when he worked undercover purchased machine guns, explosives and drugs, and nailed the sellers.

Jim Nicholson, former investigative reporter (and, later, obituary writer) for the Daily News, worked with Bill Drum when Jim was investigating outlaw bikers for the old Evening Bulletin in 1976.

"We became good friends over the years, and I learned that, beyond being a first-rate investigator, Billy was a man who was deeply devoted to his family and to his church," Nicholson said.

Bill Drum was born in Philadelphia to William Drum and the former Cecilia Sweeney. He graduated from La Salle College High School and St. Joseph's University.

He served as a medical corpsman attached to the Marine Corps in the South Pacific. "He always thought of himself as a Marine," said his son Denis Drum. "But he never talked much about his experiences."

Bill was an ordained deacon at St. Jude's Church, in Blackwood. "He had to study theology to get that position," Denis said. "He was very committed to his church. He baptized all his grandchildren."

After his retirement from ATF, Bill worked for 10 years in security for Harrah's.

He was a 4th degree member of the Knights of Columbus.

Bill is survived by his wife of 47 years, the former Dolores Jane Ryan; another son, Kevin Drum; a daughter, Eileen Marie Ploski; three sisters, Marie Glickman, Rita Patricia Maguire and Helen Quigley; and five grandchildren.

Services: Funeral Mass 10 a.m. today at St. Jude's Church, 401 S. Black Horse Pike, Blackwood. Friends may call at 8:45 a.m. Burial will be in New St. Mary's Cemetery, Bellmawr.

In lieu of flowers, donations may be made to the St. Jude/St. Agnes St. Vincent DePaul Society, 701 Little Gloucester Rd., Blackwood NJ 08012.