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GMC 454 specs: 454 ci (7.4L) 8-cylinder, 4.25 x 4.00 in (108 x 101.6 mm) bore and stroke, 8:1 compression. Rated 230 hp. OHV. Rod ratio and piston speed.
The GMC Big Block Chevy (454) is oversquare — the 4.25" 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. Each of the 8 cylinders displaces 56.8 ci (930 cc).
8:1 on iron heads is low by modern standards and generally happy on regular pump fuel.
It is one of 5 engines in the Big Block Chevy family, sitting between the 396 ci and 502 ci members. Factory fitments include the GMC C/K Series, GMC Suburban, GMC Vandura.
| Displacement | 454 ci / 7.4 L |
|---|---|
| Bore | 4.25" |
| Stroke | 4" |
| Cylinders | 8 |
| Compression ratio | 8:1 |
| Bore/stroke ratio | 1.063 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 230 hp |
| 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 |
| Displacement per cylinder | 56.8 ci |
| Static compression | 8:1 — low by modern standards, generally happy on regular pump fuel |
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