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Chevrolet 427ci specs: 427 ci (7.0L) 8-cylinder, 4.25 x 3.766 in (108 x 95.7 mm) bore and stroke, 11:1 compression. Rated 425-435 hp, 1966–1969.
The Chevrolet 427ci is oversquare — the 4.25" bore exceeds the 3.766" stroke by 12.9% — a layout that favors airflow and RPM over leverage at the crank. The 3.766" 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 1.629 is in the range most production engines fall in. Each of the 8 cylinders displaces 53.4 ci (875 cc).
11:1 is high enough that pump premium or better is normally required.
It is one of 7 engines in the Chevrolet 427ci family, all of them 427 ci — the differences between them are in compression, heads and rating, not displacement. 7 factory variants share these dimensions, rated from 425 to 435 hp across 1966–1969.
| Displacement | 427 ci / 7 L |
|---|---|
| Bore | 4.25" |
| Stroke | 3.766" |
| Cylinders | 8 |
| Compression ratio | 11:1 |
| Rod length | 6.136" |
| Rod ratio | 1.629 |
| Bore/stroke ratio | 1.129 |
| Piston deck clearance | 0.008" |
| Induction | 1-4 |
|---|---|
| Advertised HP | 425–435 hp |
| Years | 1966–1969 |
| Bore/stroke character | 1.129 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,766 ft/min — in the range typical of performance street engines |
| Rod ratio | 1.629 — moderate — the range most production V8s fall in |
| Displacement per cylinder | 53.4 ci |
| Static compression | 11:1 — high enough that pump premium or better is normally required |
| Intake valve diameter | 2.195" |
|---|---|
| Exhaust valve diameter | 1.845" |
| Chamber volume | 106.9 cc |
| Rocker ratio | 1.7:1 |
| Lifter type | mechanical |
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 | — |
| 1967 | 435 hp | — |
| 1968 | 425 hp | — |
| 1968 | 435 hp | — |
| 1969 | 425 hp | — |
| 1969 | 435 hp | — |