Chevrolet 427ci 12.5:1 Specs
Chevrolet Chevrolet 427ci · 4.25" × 3.766" · 12.5:1 engine specs: 427 ci (7L), 8-cylinder, 4.25" bore x 3.766" stroke, 12.5:1 compression.
Dimensions
| Displacement | 427 ci / 7 L |
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| Bore | 4.25" |
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| Stroke | 3.766" |
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| Cylinders | 8 |
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| Compression ratio | 12.5:1 |
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| Rod length | 6.136" |
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| Rod ratio | 1.629 |
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| Bore/stroke ratio | 1.129 |
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| Piston deck clearance | 0.002" |
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Construction
| Induction | 1-4 |
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| Advertised HP | 430 hp |
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| Years | 1968 |
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What these numbers mean
| Bore/stroke character | 1.129 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
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| Mean piston speed at 6,000 RPM | 3,766 ft/min — in the range typical of performance street engines |
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| Rod ratio | 1.629 — moderate — the range most production V8s fall in |
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| Displacement per cylinder | 53.4 ci |
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| Static compression | 12.5:1 — high enough that pump premium or better is normally required |
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Cylinder head
| Intake valve diameter | 2.195" |
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| Exhaust valve diameter | 1.845" |
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| Chamber volume | 103.3 cc |
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| Rocker ratio | 1.7:1 |
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| Lifter type | mechanical |
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Similar engines
Source: NHRA blueprints — nhra.net blueprints
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