PORSCHE RACING HISTORYRobert Overby (USA)
1980
22 March 1980 - Sebring 12 Hours - World Challenge for Endurance Drivers
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 28 | Porsche 911 S | GTO | Robert Overby (USA)/Joseph Hamilton (USA)/Herb Forrest (USA) | Hamilton House Racing (USA) | 75th | 33rd | 32nd | 12 laps - DNF |
5 July 1980 - Watkins Glen 6 Hours - World Championship for Makes
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 26 | Porsche 911 SC Targa | Trans Am | Robert Overby (USA)/Frank Harmstad (USA) | Robert Overby | 27th | 12th | 33rd | 72 laps - Engine |