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Chevrolet LS4 specs: 454 ci (7.4L) 8-cylinder, 4.251 x 4.00 in (108 x 101.6 mm) bore and stroke. Rated 225-345 hp, 1970–1976. Used in the Chevrolet Bel Air.
The Chevrolet 454ci (LS4) is oversquare — the 4.251" 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. A rod ratio of 1.534 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 56.8 ci (930 cc).
It is one of 11 engines in the Chevrolet 454ci family, all of them 454 ci — the differences between them are in compression, heads and rating, not displacement. 3 factory variants share these dimensions, rated from 225 to 345 hp across 1970–1976.
| Displacement | 454 ci / 7.4 L |
|---|---|
| Bore | 4.251" |
| Stroke | 4" |
| Cylinders | 8 |
| Configuration | V8 |
| Rod length | 6.136" |
| Rod ratio | 1.534 |
| Bore/stroke ratio | 1.063 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 225–345 hp |
| Years | 1970–1976 |
| 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 |
| Rod ratio | 1.534 — short — more side loading and piston dwell at TDC, typical of stroker combinations |
| 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 |
|---|---|---|
| 1970 | 345 hp | LS4 |
| 1973 | 275 hp | LS4 |
| 1976 | 225 hp | LS4 |