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Porsche M28/01 specs: 4.5L (274.6 ci) 8-cylinder, 95 x 78.9 mm (3.7402 x 3.1063 in) bore and stroke, 8.5:1 compression. Rated 240 hp. SOHC.
The Porsche M28/01 is oversquare — the 3.7402" bore exceeds the 3.1063" stroke by 20.4% — a layout that favors airflow and RPM over leverage at the crank. The 3.1063" stroke does not reach 4,000 ft/min of mean piston speed until about 7,750 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 8 cylinders displaces 34.3 ci (562 cc).
8.5:1 on aluminum heads is low by modern standards and generally happy on regular pump fuel.
Factory fitments include the 928.
| Displacement | 274.6 ci / 4.5 L |
|---|---|
| Bore | 3.7402" |
| Stroke | 3.1063" |
| Cylinders | 8 |
| Compression ratio | 8.5:1 |
| Bore/stroke ratio | 1.204 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | SOHC |
| Fuel type | gas |
| Advertised HP | 240 hp |
| Bore/stroke character | 1.204 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,106 ft/min — conservative for a street engine |
| Displacement per cylinder | 34.3 ci |
| Static compression | 8.5:1 — low by modern standards, generally happy on regular pump fuel |
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