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Chevrolet 427ci 4.125" bore specs: 427 ci (7.0L) 8-cylinder, 4.125 x 4.00 in (104.8 x 101.6 mm) bore and stroke. Rated 425-470 hp, 2012–2023. OHV.
The Chevrolet 427ci 4.125" bore is close to square: 4.125" bore against 4" stroke, within 3.1%, which splits the difference between a high-revving layout and a torque layout. The 4" stroke puts mean piston speed at 4,000 ft/min around 6,000 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.525 is short — higher piston acceleration and more side-load, typical of stroker combinations and a reason to watch piston speed closely. Each of the 8 cylinders displaces 53.4 ci (875 cc).
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. 13 factory variants share these dimensions, rated from 425 to 470 hp across 2012–2023.
| Displacement | 427 ci / 7 L |
|---|---|
| Bore | 4.125" |
| Stroke | 4" |
| Cylinders | 8 |
| Configuration | V8 |
| Rod length | 6.1" |
| Rod ratio | 1.525 |
| Bore/stroke ratio | 1.031 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 425–470 hp |
| Years | 2012–2023 |
| Bore/stroke character | 1.031 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 4,000 ft/min — in the range typical of performance street engines |
| Rod ratio | 1.525 — short — more side loading and piston dwell at TDC, typical of stroker combinations |
| Displacement per cylinder | 53.4 ci |
| Intake valve diameter | 2.205" |
|---|---|
| Exhaust valve diameter | 1.615" |
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 |
|---|---|---|
| 2012 | 425 hp | — |
| 2013 | 425 hp | — |
| 2014 | 430 hp | — |
| 2014 | 450 hp | — |
| 2015 | 430 hp | — |
| 2015 | 450 hp | — |
| 2016 | 470 hp | — |
| 2017 | 470 hp | — |
| 2018 | 470 hp | — |
| 2019 | 470 hp | — |
| 2020 | 470 hp | — |
| 2022 | 470 hp | — |
| 2023 | 470 hp | — |