With the score 3-3 after Jose Luis Cilley and Henry Honiball exchanged penalties, Gonzalo Camardon broke through for a try after 35 minutes to put Argentina ahead but Puma mistakes allowed Andre Venter and Mark Andrews to score tries, both converted by Honiball, in the last four minutes of the half to put South Africa ahead 17-8 at the interval.
Hennie Le Roux opened the second half with an unconverted try and then a penalty try, converted by Honiball, put South Africa ahead 29-8 after 62 minutes. Rolando Martin scored the Pumas' last try, converted by Cilley. That was as close as they got with James Small, Joost van der Westhuizen, and Andre Joubert touching down for the visitors.
Western Samoa will field four new caps against Ireland at Lansdowne Road tomorrow, including the former All Black Va'aiga Tuigamala, who played his first match for his native country in Saturday's 35-25 win over Munster.
The other newcomers are the right wing Osato So'oala, outside-half Earl Va'a and loose forward Isaac Feaunati.
Junior Paramore, the former rugby league player who is now with Bedford, is on the bench. Paramore and Tuigamala were called into the touring party last week.
Nick Popplewell, Ireland's loose head prop, has been ruled out of the game because of a hamstring strain sustained during training on Saturday. He is replaced by Moseley's Henry Hurley.
Scott Quinnell is reported to have settled his pay dispute with the Welsh Rugby Union. The Richmond No 8 is expected to sign a contract this week which will revive hopes of a Wales recall against Australia on 1 December.
Only last week Quinnell maintained that he was unlikely to play for Wales this season following the breaking-off of negotiations with Terry Cobner, the WRU director of rugby.