Pontiac 389ci 8.6:1 Specs
Pontiac Pontiac 389ci · 4.062" × 3.75" · 8.6:1 engine specs: 389 ci (6.4L), 8-cylinder, 4.062" bore x 3.75" stroke, 8.6:1 compression.
Dimensions
| Displacement | 389 ci / 6.4 L |
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| Bore | 4.062" |
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| Stroke | 3.75" |
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| Cylinders | 8 |
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| Compression ratio | 8.6:1 |
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| Rod length | 6.625" |
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| Rod ratio | 1.767 |
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| Bore/stroke ratio | 1.083 |
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| Piston deck clearance | 0" |
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Construction
| Induction | 1-2 |
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| Advertised HP | 215–256 hp |
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| Years | 1959–1966 |
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What these numbers mean
| Bore/stroke character | 1.083 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
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| Mean piston speed at 6,000 RPM | 3,750 ft/min — in the range typical of performance street engines |
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| Rod ratio | 1.767 — long — less side loading on the cylinder wall, favours high RPM |
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| Displacement per cylinder | 48.6 ci |
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| Static compression | 8.6:1 — low by modern standards, generally happy on regular pump fuel |
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Cylinder head
| Intake valve diameter | 1.88" |
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| Exhaust valve diameter | 1.6" |
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| Chamber volume | 74.7 cc |
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| Rocker ratio | 1.5:1 |
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| Lifter type | hydraulic |
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Variants sharing these dimensions (16)
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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| 1959 | 215 hp | — |
| 1960 | 215 hp | — |
| 1960 | 230 hp | — |
| 1961 | 215 hp | — |
| 1961 | 230 hp | — |
| 1961 | 235 hp | — |
| 1962 | 215 hp | — |
| 1962 | 230 hp | — |
| 1962 | 235 hp | — |
| 1963 | 215 hp | — |
| 1963 | 230 hp | — |
| 1963 | 235 hp | — |
| 1964 | 230 hp | — |
| 1964 | 235 hp | — |
| 1965 | 256 hp | — |
| 1966 | 256 hp | — |
Similar engines
Source: NHRA blueprints — nhra.net blueprints
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