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GMC Big Block Chevy (1968–1969) specs: 396 ci (6.5L) 8-cylinder, 4.094 x 3.76 in (104 x 95.5 mm) bore and stroke. Built 1968–1969. Used in the GMC C/K Pickup.
The GMC Big Block Chevy (1968–1969) is oversquare — the 4.094" bore exceeds the 3.76" stroke by 8.9% — a layout that favors airflow and RPM over leverage at the crank. The 3.76" stroke puts mean piston speed at 4,000 ft/min around 6,400 RPM, which is where a production bottom end is generally considered at its limit. A rod ratio of 1.632 is in the range most production engines fall in. Each of the 8 cylinders displaces 49.5 ci (811 cc).
It is one of 11 engines in the Big Block Chevy family, the smallest at 396 ci. 2 factory variants share these dimensions across 1968–1969.
| Displacement | 396 ci / 6.5 L |
|---|---|
| Bore | 4.094" |
| Stroke | 3.76" |
| Cylinders | 8 |
| Configuration | V8 |
| Rod length | 6.135" |
| Rod ratio | 1.632 |
| Bore/stroke ratio | 1.089 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Firing order | 1-8-4-3-6-5-7-2 |
| Years | 1968–1969 |
| Bore/stroke character | 1.089 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,760 ft/min — in the range typical of performance street engines |
| Rod ratio | 1.632 — moderate — the range most production V8s fall in |
| Displacement per cylinder | 49.5 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 |
|---|---|---|
| 1968 | — | — |
| 1969 | — | — |
1 factory vehicle, 1968–1969. Each year opens that model's engine table.