PORSCHE RACING HISTORYMike Schaefer (USA)
1983 : Daytona 24 Hours - 2nd in class
6 February 1983 - Daytona 24 Hours - IMSA - International Motor Sport Association
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 90 | Porsche 911 SC | 911 030 1263 | GTU | Mike Schaefer (USA)/Jack Refenning (USA)/John Belperche (USA)/Doug Zitza (USA) | 901 Shop | 14th | 2nd | 70th | 525 laps |
19 March 1983 - Sebring 12 Hours - IMSA - International Motor Sport Association
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 90 | Porsche 911 SC | 911 030 1263 | GTU | Mike Schaefer (USA)/Doug Zitza (USA)/Jack Refenning (USA) | 901 Shop | 22nd | 8th | 63rd | 198 laps |
1 May 1983 - Trans-Am Moroso - Trans-Am
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 90 | Porsche 911 SC | 911 030 1263 | Mike Schaefer (USA) | 901 Shop (USA) | 18th | 36th | 40 laps |
3 July 1983 - Daytona 250 Miles Paul Revere - IMSA - International Motor Sport Association
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 90 | Porsche 911 SC | 911 030 1263 | GTU | Mike Schaefer (USA)/Ren Tilton (USA) | 901 Shop | 21st | 6th | 36th | 55 laps |
27 November 1983 - Daytona Finale 3 Hours - IMSA - International Motor Sport Association
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 90 | Porsche 911 SC | 911 030 1263 | GTU | Mike Schaefer (USA)/Tom Sheehy (USA) | 901 Shop | 28th | 8th | 52nd | 77 laps |