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Ford 281ci specs: 281 ci (4.6L) 8-cylinder, 3.553 x 3.543 in (90.2 x 90 mm) bore and stroke, 11:1 compression. Rated 235 hp, 2010. Rod ratio and piston speed.
The Ford 281ci is close to square: 3.553" bore against 3.543" stroke, within 0.3%, which splits the difference between a high-revving layout and a torque layout. The 3.543" stroke puts mean piston speed at 4,000 ft/min around 6,750 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.675 is in the range most production engines fall in. Each of the 8 cylinders displaces 35.1 ci (576 cc).
11:1 is high enough that pump premium or better is normally required.
It is one of 21 engines in the Ford 281ci family, all of them 281 ci — the differences between them are in compression, heads and rating, not displacement.
| Displacement | 281 ci / 4.6 L |
|---|---|
| Bore | 3.553" |
| Stroke | 3.543" |
| Cylinders | 8 |
| Compression ratio | 11:1 |
| Rod length | 5.933" |
| Rod ratio | 1.675 |
| Bore/stroke ratio | 1.003 |
| Piston deck clearance | 0.01" |
| Advertised HP | 235 hp |
|---|---|
| Years | 2010 |
| Bore/stroke character | 1.003 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,543 ft/min — in the range typical of performance street engines |
| Rod ratio | 1.675 — moderate — the range most production V8s fall in |
| Displacement per cylinder | 35.1 ci |
| Static compression | 11:1 — high enough that pump premium or better is normally required |
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