Frank Bank ( April 12 , 1942 -- April 13 , 2013 ) was an American actor , particularly known for his role as Clarence `` Lumpy '' Rutherford on the 1957 -- 1963 situation comedy television series `` Leave It to Beaver '' .
Frank Bank ( April 12 , 1942 -- April 13 , 2013 ) was an American actor . He was best known for his role as Clarence `` Lumpy '' Rutherford on the situation comedy television series `` Leave It to Beaver '' .