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Chevrolet L8T specs: 400.6 ci (6.6L) 8-cylinder, 4.065 x 3.858 in (103.3 x 98 mm) bore and stroke, 10.8:1 compression. Rated 401 hp. OHV.
The Chevrolet Gen V LT (L8T) is oversquare — the 4.065" bore exceeds the 3.8583" stroke by 5.4% — a layout that favors airflow and RPM over leverage at the crank. The 3.8583" stroke puts mean piston speed at 4,000 ft/min around 6,200 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 50.1 ci (821 cc).
10.8:1 on aluminum heads is in the range that usually runs on pump premium; aluminum sheds heat faster than iron, which makes the same number a little more forgiving.
It is one of 14 engines in the Gen V LT family, the largest at 400.6 ci. Factory fitments include the Chevrolet Silverado 2500HD/3500HD, GMC Sierra 2500HD/3500HD.
| Displacement | 400.6 ci / 6.6 L |
|---|---|
| Bore | 4.065" |
| Stroke | 3.8583" |
| Cylinders | 8 |
| Compression ratio | 10.8:1 |
| Bore/stroke ratio | 1.054 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 401 hp |
| Bore/stroke character | 1.054 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,858 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 50.1 ci |
| Static compression | 10.8:1 — in the range that usually runs on pump premium |
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