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Ford S-code specs: 390 ci (6.4L) 8-cylinder, 4.052 x 3.784 in (102.9 x 96.1 mm) bore and stroke. Rated 320-335 hp, 1966–1967. Used in the Ford Fairlane.
The Ford S-code is oversquare — the 4.052" bore exceeds the 3.784" stroke by 7.1% — a layout that favors airflow and RPM over leverage at the crank. The 3.784" stroke puts mean piston speed at 4,000 ft/min around 6,350 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.715 is in the range most production engines fall in. Each of the 8 cylinders displaces 48.8 ci (799 cc).
It is one of 21 engines in the Ford 390ci family, all of them 390 ci — the differences between them are in compression, heads and rating, not displacement. 2 factory variants share these dimensions, rated from 320 to 335 hp across 1966–1967.
| Displacement | 390 ci / 6.4 L |
|---|---|
| Bore | 4.052" |
| Stroke | 3.784" |
| Cylinders | 8 |
| Configuration | V8 |
| Rod length | 6.488" |
| Rod ratio | 1.715 |
| Bore/stroke ratio | 1.071 |
| Fuel type | gas |
|---|---|
| Advertised HP | 320–335 hp |
| Years | 1966–1967 |
| Bore/stroke character | 1.071 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,784 ft/min — in the range typical of performance street engines |
| Rod ratio | 1.715 — moderate — the range most production V8s fall in |
| Displacement per cylinder | 48.8 ci |
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These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1966 | 335 hp | S-code |
| 1967 | 320 hp | S-code |