Trim crust from pound cake and cut cake into 1" cubes. Combine 2/3 cup sugar and coffee in a small saucepan; bring to a boil over medium heat, stirring frequently. Boil 1 minute. Remove from heat and let cool 1 minute. Stir in Kahlúa. Pour coffee syrup mixture into a small bowl and let cool completely.
Combine pecans and 1/4 cup sugar; stir well. Working quickly, dip each cake cube into coffee syrup. Roll each cube in pecan mixture, coating completely. Let cake cubes dry at room temperature on wire racks at least 2 hours.