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Chevrolet L18 Vortec 8100 specs: 496 ci (8.1L) 8-cylinder, 4.25 x 4.37 in (108 x 111 mm) bore and stroke, 9.1:1 compression. Rated 325 hp, 2003–2008.
The Chevrolet L18 Vortec 8100 is close to square: 4.25" bore against 4.37" stroke, within 2.7%, which splits the difference between a high-revving layout and a torque layout. With a 4.37" stroke, mean piston speed reaches 4,000 ft/min at only 5,500 RPM — the practical ceiling for a production bottom end — which is why a stroke this long makes its power low and runs out of safe revs early. Each of the 8 cylinders displaces 62.0 ci (1,016 cc).
9.1:1 on iron heads is low by modern standards and generally happy on regular pump fuel.
It is one of 3 engines in the Vortec 8100 family, all of them 496 ci — the differences between them are in compression, heads and rating, not displacement. 2 factory variants share these dimensions, rated at 325 hp across 2003–2008.
| Displacement | 496 ci / 8.1 L |
|---|---|
| Bore | 4.25" |
| Stroke | 4.37" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 9.1:1 |
| Bore/stroke ratio | 0.973 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Firing order | 1-8-7-2-6-5-4-3 |
| Advertised HP | 325 hp |
| Years | 2003–2008 |
| Bore/stroke character | 0.973 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 4,370 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 62.0 ci |
| Static compression | 9.1:1 — low by modern standards, generally happy on regular pump fuel |
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 |
|---|---|---|
| 2003 | 325 hp | L18 Vortec 8100 |
| 2008 | 325 hp | L18 Vortec 8100 |
1 factory vehicle, 2003–2008. Each year opens that model's engine table.