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Honda J25A specs: 2.5L (152.6 ci) 6-cylinder, 86 x 71.6 mm (3.3858 x 2.8189 in) bore and stroke, 10:1 compression. Rated 200 hp. Rod ratio and piston speed.
The Honda J25A is oversquare — the 3.3858" bore exceeds the 2.8189" stroke by 20.1% — a layout that favors airflow and RPM over leverage at the crank. The 2.8189" stroke does not reach 4,000 ft/min of mean piston speed until about 8,500 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 25.4 ci (417 cc).
10:1 on aluminum heads is in the range that usually runs on pump premium; aluminum sheds heat faster than iron, which makes the same number a little more forgiving.
It is one of 13 engines in the J-series V6 family, the smallest at 152.6 ci. Factory fitments include the Honda Inspire, Honda Saber.
| Displacement | 152.6 ci / 2.5 L |
|---|---|
| Bore | 3.3858" |
| Stroke | 2.8189" |
| Cylinders | 6 |
| Compression ratio | 10:1 |
| Bore/stroke ratio | 1.201 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | SOHC |
| Fuel type | gas |
| Advertised HP | 200 hp |
| Bore/stroke character | 1.201 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 2,819 ft/min — conservative for a street engine |
| Displacement per cylinder | 25.4 ci |
| Static compression | 10:1 — in the range that usually runs on pump premium |
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