PORSCHE RACING HISTORYMark Altman (USA)
1987
21 March 1987 - Sebring 12 Hours - IMSA - International Motor Sport Association
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 13 | Porsche 914/6 | GTU | Gary Altman (USA)/Mark Altman (USA)/Tim Selby (USA) | Altman Bros. Motor Racing (USA) | 59th | 15th | 60th | 68 laps - Gearbox |
7 June 1987 - Mid-Ohio 250 km IMSA GTO - IMSA - International Motor Sport Association
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 20 | Porsche 914/6 | GTU | Mark Altman (USA) | Altman Bros Racing (USA) | 28th | 15th | 29th | 56 laps - DNF |
16 August 1987 - Road America 500 Miles - IMSA - International Motor Sport Association
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 20 | Porsche 914/6 | GTU | Mark Altman (USA)/Gary Altman (USA) | Altman Bros. Motor Racing (USA) | 28th | 6th | 51st | 66 laps |
4 October 1987 - Columbus IMSA GT - IMSA - International Motor Sport Association
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 20 | Porsche 914/6 | GTU | Mark Altman (USA) | Altman Bros. Racing (USA) | 40th | 17th | 34th | 0 laps - DNF |