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GMC LS4 specs: 454 ci (7.4L) 8-cylinder, 4.25 x 4.00 in (108 x 101.6 mm) bore and stroke. Built 1973–1975. Used in the Chevrolet Caprice and Chevrolet Impala.
The GMC Big Block Chevy (LS4) is oversquare — the 4.25" bore exceeds the 4" stroke by 6.3% — a layout that favors airflow and RPM over leverage at the crank. 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. Each of the 8 cylinders displaces 56.8 ci (930 cc).
It is one of 11 engines in the Big Block Chevy family, sitting between the 396 ci and 502 ci members. 3 factory variants share these dimensions across 1973–1975.
| Displacement | 454 ci / 7.4 L |
|---|---|
| Bore | 4.25" |
| Stroke | 4" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 8.15–8.25:1 (published figures vary) |
| Bore/stroke ratio | 1.063 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Firing order | 1-8-4-3-6-5-7-2 |
| Years | 1973–1975 |
| Bore/stroke character | 1.063 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 4,000 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 56.8 ci |
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 |
|---|---|---|
| 1973 | — | LS4 |
| 1974 | — | LS4 |
| 1975 | — | LS4 |
11 factory vehicles, 1970–1976. Each year opens that model's engine table.