Shelby 428ci 12.25:1 Specs
Shelby Shelby 428ci · 4.132" × 3.984" · 12.25:1 engine specs: 428 ci (7L), 8-cylinder, 4.132" bore x 3.984" stroke, 12.25:1 compression.
Dimensions
| Displacement | 428 ci / 7 L |
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| Bore | 4.132" |
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| Stroke | 3.984" |
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| Cylinders | 8 |
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| Compression ratio | 12.25:1 |
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| Rod length | 6.488" |
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| Rod ratio | 1.629 |
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| Bore/stroke ratio | 1.037 |
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| Piston deck clearance | 0.005" |
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Construction
| Induction | 2-4 |
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| Advertised HP | 390 hp |
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| Years | 1967 |
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What these numbers mean
| Bore/stroke character | 1.037 — square — bore and stroke are within 5%, a balanced compromise |
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| Mean piston speed at 6,000 RPM | 3,984 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 | 53.5 ci |
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| Static compression | 12.25:1 — high enough that pump premium or better is normally required |
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Cylinder head
| Intake valve diameter | 2.037" |
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| Exhaust valve diameter | 1.566" |
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| Chamber volume | 65 cc |
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| Rocker ratio | 1.73:1 |
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| Lifter type | mechanical |
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Similar engines
Source: NHRA blueprints — nhra.net blueprints
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