PORSCHE RACING HISTORYMark Greb (USA)
1978 : Daytona 24 Hours - 2nd in class : Mid Ohio 250 Miles - 3rd in class
5 February 1978 - Daytona 24 Hours - World Championship for Makes
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 34 | Porsche 911 S | GTU | George Drolsom (USA)/Hugh Davenport (USA)/Mark Greb (USA) | Drolsom Racing (USA) | 12th | 2nd | 57th | 592 laps |
27 August 1978 - Mid Ohio 250 Miles - IMSA - International Motor Sport Association
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 34 | Porsche 911 S | GTU | George Drolsom (USA)/Mark Greb (USA) | Drolsom Racing (USA) | 17th | 3rd | 35th | 93 laps |