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Porsche M97 specs: 3.8L (233.3 ci) 6-cylinder, 99 x 82.8 mm (3.8976 x 3.2598 in) bore and stroke. Rated 355 hp, 2005–2008. Used in the Porsche 911. DOHC.
The Porsche M97 (M97) is oversquare — the 3.8976" bore exceeds the 3.2598" stroke by 19.6% — a layout that favors airflow and RPM over leverage at the crank. The 3.2598" stroke does not reach 4,000 ft/min of mean piston speed until about 7,350 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 38.9 ci (637 cc).
It is one of 2 engines in the M97 family, all of them 233.3 ci — the differences between them are in compression, heads and rating, not displacement. 4 factory variants share these dimensions, rated at 355 hp across 2005–2008.
| Displacement | 233.3 ci / 3.8 L |
|---|---|
| Bore | 3.8976" |
| Stroke | 3.2598" |
| Cylinders | 6 |
| Bore/stroke ratio | 1.196 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 355 hp |
| Years | 2005–2008 |
| Bore/stroke character | 1.196 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,260 ft/min — conservative for a street engine |
| Displacement per cylinder | 38.9 ci |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 2005 | 355 hp | M97 |
| 2006 | 355 hp | M97 |
| 2007 | 355 hp | M97 |
| 2008 | 355 hp | M97 |