The Washington Federals held a tryout yesterday at RFK Stadium and signed three players from among the 618 who showed up.

Signed were defensive end Tim Swords (6-foot-3, 260 pounds) of East Carolina University, defensive back Paul McKinney (5-10, 170) from East Tennessee State and linebacker Mike Lemon (6-2, 225) of Maryland.

Swords, 25, is one of the top heavyweight weightlifters; he won a bronze medal at the National Sports Festival last year at Syracuse, N.Y. He runs 40 yards in 4.8 seconds. McKinney, 25, started two years at East Tennessee and played last year with the Carroll County Chargers of the Interstate semipro league.

Lemon, 25, played two years at Kansas State and was red-shirted when he transferred to Maryland, but quit without ever playing for the Terrapins.

Former Redskin defensive tackle (1970-'75) Manny Sistrunk tried out but was not signed. The Federals now have 40 under contract . . .

With quarterback Condredge Holloway leading the way, the Toronto Argonauts won their first Canadian Football League East conference championship since 1971 by defeating the Rough Riders, 28-14, in Ottawa . . .

Twelve of the nation's top college football linemen were nominated to receive the 13th Annual Lombardi Award. Nominated were George Achica from Southern California, Charles Benson, Baylor; Tim Krumrie, Wisconsin; Wilber Marshall, Florida; Bruce Matthews, Southern California; and Don Mosebar, Southern California. Also selected were Jimbo Covert, Pittsburgh; Vernon Maxwell, Arizona State; Mike Pitts, Alabama; Dave Rimington, Nebraska; Billy Ray Smith, Arkansas; and Darryl Talley, West Virginia. Four finalists will be picked later this month . . .

Mike Royko, Chicago Sun-Times columnist, was asked on the Phil Donahue show what he thought of the NFL strike, and Royko replied: "You really should ask that of somebody from a city that has a pro football team" . . .