Pontiac 421 Specs
Pontiac 421 engine specs: 421 ci (6.9L), 8-cylinder, 4.0906" bore x 4" stroke, 10.75:1 compression.
Dimensions
| Displacement | 421 ci / 6.9 L |
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| Bore | 4.0906" |
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| Stroke | 4" |
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| Cylinders | 8 |
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| Compression ratio | 10.75:1 |
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| Bore/stroke ratio | 1.023 |
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Construction
| Block material | cast iron |
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| Head material | cast iron |
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| Valvetrain | OHV |
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| Fuel type | gas |
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| Advertised HP | 376–405 hp |
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What these numbers mean
| Bore/stroke character | 1.023 — square — bore and stroke are within 5%, a balanced compromise |
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| Mean piston speed at 6,000 RPM | 4,000 ft/min — in the range typical of performance street engines |
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| Displacement per cylinder | 52.6 ci |
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| Static compression | 10.75:1 — in the range that usually runs on pump premium |
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Variants sharing these dimensions (2)
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
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| — | 376 hp | 421 |
| — | 405 hp | 421 |
Vehicles (5)
- Pontiac Grand Prix
- Pontiac Catalina 2+2
- Grand Prix
- Catalina 2+2
- Bonneville
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