Don Kirwin of Landon dashed off a 2:08 final half-mile en route to a 9:17.3 clocking to win the two-mile run tonight, highlighting the Naval Academy Invitational at Halsey Field House.

Kirwin took the lead from runner-up Doug Halpin of Peary (9:27.0) in the last 600 yards and cruised to a 40-yard lead. Pat McCoy of Oakton, the prerace favorite with Kirwin, was third in 9:29.6.

The meet was dominated by slower-than-usual performances and wins by southern Virginia and Philadelphia trackmen.

Todd Colas of Osbourn Park took the mile event in 4:19.5. Colas, whose brother Tim was the mild champion the last two years, held off fast-closing Dwight Stephens of T. C. Williams, who will run the mile in the Milrose Games in Madison Square Garden next Saturday.

Desmond DaCosta of Philadelphia's Overbrook cleared 6-feet-10 1/2 to win the high jump. Bob Smith of Westminster and Scott Dunham of Central also topped 6-10 1/2 to up the meet mark by a quarter-inch.

The St. Albans foursome of Ramon Ruiz, Bruce Randolph, Steve Washington and Ray Brown claimed the distance medley (10:25.0) over Lake Braddock (10:30.0).

Sandy Chapman's 1:53.7 anchor leg for Spingarn's two-mile relay was the fastest split of the event, but Spingarn (8:01.5) managed only third place behind Central of Philadelphia 7:58.8) and Jefferson-Hugenot-Wythe (8:00.6).