| Final | time | | 1. Malvin Whitfield |  United States | 47.8s | | 2. Hugo Maiocco | United States | 48.0s | | 3. Herb McKenley |  Jamaica | 48.2s | | 4. John Voight | United States | 48.3s | | 5. Angel Garcia Delgado |  Cuba | 48.4s | | 6. Gustavo Ehlers Trostel |  Chile | 49.4s |
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| Semi 1 | time | | 1. Angel Garcia Delgado | Cuba | 48.5s | | 2. John Voight | United States | 48.9s | | 3. Gustavo Ehlers Trostel | Chile | 48.9s | | 4. Carlos Monges Caldera |  Mexico | 49.8s | | 5. Guillermo Evans |  Argentina | 50.8s | | 6. Ramón Sandoval | Chile | |
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| Semi 2 | time | | 1. Malvin Whitfield | United States | 48.1s | | 2. Herb McKenley | Jamaica | 48.9s | | 3. Hugo Maiocco | United States | 49.0s | | 4. Jaime Hitelman Reitich | Chile | 49.5s | | 5. Guido Veronese | Argentina | 49.7s | | 6. Máximo Guerra | Argentina | |
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| Heat 1 | time | | 1. John Voight | United States | 50.6s | | 2. Angel Garcia Delgado | Cuba | 50.6s | | 3. Ramón Sandoval | Chile | 50.7s | | 4. Carlos Camargo Leon | Mexico | 51.2s | | 5. Anastasio Zelaya |  Paraguay | 51.5s | | 6. Luis Modeste |  Trinidad Tobago | |
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| Heat 2 | time | | 1. Guillermo Evans | Argentina | 57.3s | | 2. Gustavo Ehlers Trostel | Chile | 57.4s | | 3. Carlos Monges Caldera | Mexico | 1:04.9 | | -. Argemiro Roque |  Brazil | DNS | | -. Evelio Planas del Rio | Cuba | DNS |
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| Heat 3 | time | | 1. Herb McKenley | Jamaica | 49.0s | | 2. Hugo Maiocco | United States | 50.0s | | 3. Guido Veronese | Argentina | 50.2s | | 4. José Zelaya del Pilar | Paraguay | 50.5s | | 5. Javier Sousa Diaz | Mexico | 50.6s |
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| Heat 4 | time | | 1. Mal Whitfield | United States | 49.2s | | 2. Jaime Hitelman Reitich | Chile | 50.6s | | 3. Máximo Guerra | Argentina | 50.6s | | 4. Guillermo Gutiérrez |  Venezuela | 51.2s | | -. Jacinto Gonzalez Patterson |  Ecuador | DNS |
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