Mike Toomey of Alexandria, Va., and Dave King of Bethesda, Md., made impressive showings in the first round of the U.S. Amateur golf championship today at famed Aronimink Golf Club.

Toomey, three down to Walker Cup standout Vance Heafner of Cary, N.C., posted a 1-up victory. Toomey won the 11 and 12th with pars and birdied the par-three 14th and 17th. On the final hole Heafner's birdie putt from 12 feet hung on the lower lip of the cup and Toomey sank a four-foot par putt.

King, four up at nine, beat H. B. Warren II of Tulsa, 5 and 3.

Gary Mankulish, Maryland and District of Columbia Amateur champ from Prince Georges Country Club, played in one of 16 matches halted by rain. He was two up with three holes to play.

Jim Fitzgerald, Poolesville, Md., lost to British Walker Cup player Ian Hutcheson, Monifieth, Scotland, 4 and 2.

Martie West of Columbia Country Club, Chevy Chase Md., drew a bye and plays Doug H. Fischesser, Connersville, Ind., 1-up winner over Scott Cooke, East Greenwich, R.I. Thursday.

Toomey, 30, said, "I was so nervous that I couldn't draw the club back. I couldn't concentrate. I was trying to steer the ball on the front nine."

Defending Amateur champion Bill Sander and Bill Campbell won first-round matches in the 77th tournament. Campbell, 1964 titlist, is competing in his 35th national championship.

Another former champ, Gary Cown (1966 and 1971), won easily.

Virginians Vinny Giles of Richmond and William Sibbick, Martinsville, drew byes.