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Ford AJ30_3_9 specs: 241 ci (3.9L) 8-cylinder, 3.386 x 3.346 in (86 x 85 mm) bore and stroke. Rod ratio and piston speed worked out.
The Ford AJ30_3_9 is close to square: 3.3858" bore against 3.3465" stroke, within 1.2%, which splits the difference between a high-revving layout and a torque layout. The 3.3465" stroke does not reach 4,000 ft/min of mean piston speed until about 7,150 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 8 cylinders displaces 30.1 ci (494 cc).
It is one of 2 engines in the AJ-V8 (Jaguar) family, all of them 241 ci — the differences between them are in compression, heads and rating, not displacement.
| Displacement | 241 ci / 3.9 L |
|---|---|
| Bore | 3.3858" |
| Stroke | 3.3465" |
| Cylinders | 8 |
| Bore/stroke ratio | 1.012 |
| Fuel type | gas |
|---|
| Bore/stroke character | 1.012 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,347 ft/min — conservative for a street engine |
| Displacement per cylinder | 30.1 ci |
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