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Shelby 427ci (1966–1967) specs: 7.0L (427 ci) 8-cylinder, 107.5 x 96.1 mm (4.2320 x 3.7840 in) bore and stroke, 11.1:1 compression. Rated 425 hp, 1966–1967.
The Shelby 427ci (1966–1967) is oversquare — the 4.232" bore exceeds the 3.784" stroke by 11.8% — 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 53.4 ci (875 cc).
11.1:1 is high enough that pump premium or better is normally required.
2 factory variants share these dimensions, rated at 425 hp across 1966–1967.
| Displacement | 427 ci / 7 L |
|---|---|
| Bore | 4.232" |
| Stroke | 3.784" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 11.1:1 |
| Rod length | 6.488" |
| Rod ratio | 1.715 |
| Bore/stroke ratio | 1.118 |
| Fuel type | gas |
|---|---|
| Advertised HP | 425 hp |
| Years | 1966–1967 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. | Duration int / exh | Valve lift int / exh | LSA |
|---|---|---|---|---|---|---|---|
| 1966 | gross | 425 | — | 11.1:1 | — | — | — |
| 1967 | R gross | 425 @ 6000 | 480 lb-ft @ 3700 | 11.1:1 | 324° | 0.500" | 114° |
Factory specification sheet. Durations are the factory's advertised figures at the basis printed on the sheet, not duration at .050" lift; lobe separation is calculated from the printed valve timing.
| Bore/stroke character | 1.118 — 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 | 53.4 ci |
| Static compression | 11.1:1 — high enough that pump premium or better is normally required |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1966 | 425 hp | — |
| 1967 | 425 hp | — |
1 factory vehicle, 1966–1967. Each year opens that model's engine table.