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GMC High Feature V6 specs: 222.7 ci (3.6L) 6-cylinder, 3.74 x 3.378 in (95 x 85.8 mm) bore and stroke, 11.5:1 compression. Rated 308-335 hp. DOHC.
The GMC High Feature V6 is oversquare — the 3.7402" bore exceeds the 3.378" stroke by 10.7% — a layout that favors airflow and RPM over leverage at the crank. The 3.378" stroke does not reach 4,000 ft/min of mean piston speed until about 7,100 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 37.1 ci (608 cc).
11.5:1 on aluminum heads is high for a production gasoline engine; running a ratio like that on pump fuel depends on chamber design and fuel delivery rather than the number alone.
It is one of 6 engines in the High Feature V6 family, the largest at 222.7 ci. 2 factory variants share these dimensions, rated from 308 to 335 hp. Factory fitments include the Cadillac CT4-V, Cadillac CT5, Chevrolet Camaro and 2 others.
| Displacement | 222.7 ci / 3.6 L |
|---|---|
| Bore | 3.7402" |
| Stroke | 3.378" |
| Cylinders | 6 |
| Compression ratio | 11.5:1 |
| Bore/stroke ratio | 1.107 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 308–335 hp |
| Bore/stroke character | 1.107 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,378 ft/min — conservative for a street engine |
| Displacement per cylinder | 37.1 ci |
| Static compression | 11.5:1 — high enough that pump premium or better is normally required |
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 |
|---|---|---|
| — | 308 hp | LGZ |
| — | 335 hp | LGX |