[3] On 20 February 1967 Þórir scored a league record 57 points for KFR against ÍS, breaking Einar Bollason’s record of 49 points.
[10][11] In 1974, he won his third straight scoring title, setting a then league record in the process with 416 points.
[12] On 17 March 1980 Þórir scored 32 points[13][1] in a 100-93 victory against KR in the last game of the season, guaranteeing Valur the first place in the league and the clubs first national championship.
[14][15] From 1967 to 1977, Þórir played 46 games for the Icelandic national team.
[16] Þórir's brother, Jóhannes Magnússon, played for several seasons in the Icelandic league.