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Acura C25A specs: 2.5L (152 ci) 6-cylinder, 84 x 75 mm (3.3071 x 2.9528 in) bore and stroke, 9:1 compression. Rated 151 hp, 1986–1987.
The Acura C25A is oversquare — the 3.3071" bore exceeds the 2.9528" stroke by 12.0% — a layout that favors airflow and RPM over leverage at the crank. The 2.9528" stroke does not reach 4,000 ft/min of mean piston speed until about 8,150 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 25.3 ci (415 cc).
9:1 is low by modern standards and generally happy on regular pump fuel.
2 factory variants share these dimensions, rated at 151 hp across 1986–1987.
| Displacement | 152 ci / 2.5 L |
|---|---|
| Bore | 3.3071" |
| Stroke | 2.9528" |
| Cylinders | 6 |
| Configuration | V6 |
| Compression ratio | 9:1 |
| Bore/stroke ratio | 1.12 |
| Fuel type | gas |
|---|---|
| Redline | 6,500 rpm (factory limit) |
| Advertised HP | 151 hp |
| Years | 1986–1987 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1986 | C25A net | 151 @ 5800 | 154 lb-ft @ 4500 | 9:1 |
| 1987 | C25A net | 151 @ 5800 | 154 lb-ft @ 4500 | 9:1 |
Factory specification sheet.
| Bore/stroke character | 1.120 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 2,953 ft/min — conservative for a street engine |
| Displacement per cylinder | 25.3 ci |
| Static compression | 9:1 — low by modern standards, generally happy on regular pump fuel |
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 |
|---|---|---|
| 1986 | 151 hp | C25A |
| 1987 | 151 hp | C25A |
1 factory vehicle, 1986–1987. Each year opens that model's engine table.