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Ford 7 3 specs: 443.6 ci (7.3L) 8-cylinder, 4.11 x 4.18 in (104.4 x 106.2 mm) bore and stroke, 21.5:1 compression. Used in the Ford F-250.
The Ford IDI Diesel V8 (7 3) is close to square: 4.11" bore against 4.18" stroke, within 1.7%, which splits the difference between a high-revving layout and a torque layout. The 4.18" stroke puts mean piston speed at 4,000 ft/min around 5,750 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 55.5 ci (909 cc).
At 21.5:1 this is a compression-ignition engine: the ratio is the heat source that lights the fuel, not a knock limit to be managed.
It is one of 7 engines in the IDI Diesel V8 family, the largest at 443.6 ci.
| Displacement | 443.6 ci / 7.3 L |
|---|---|
| Bore | 4.11" |
| Stroke | 4.18" |
| Cylinders | 8 |
| Compression ratio | 21.5:1 |
| Bore/stroke ratio | 0.983 |
| Fuel type | diesel |
|---|
| Bore/stroke character | 0.983 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 4,180 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 55.5 ci |
| Static compression | 21.5:1 — high enough that pump premium or better is normally required |
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1 factory vehicle, 1988–1994. Each year opens that model's engine table.