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Pontiac 326 specs: 326 ci (5.3L) 8-cylinder, 3.811 x 3.563 in (96.8 x 90.5 mm) bore and stroke, 8.6:1 compression. Rated 250 hp. Rod ratio and piston speed.
The Pontiac V8 (326) is oversquare — the 3.811" bore exceeds the 3.563" stroke by 7.0% — a layout that favors airflow and RPM over leverage at the crank. The 3.563" stroke puts mean piston speed at 4,000 ft/min around 6,750 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 40.8 ci (668 cc).
8.6:1 on iron heads is low by modern standards and generally happy on regular pump fuel.
It is one of 13 engines in the Pontiac V8 family, the smallest at 326 ci. Factory fitments include the Pontiac Tempest, Pontiac LeMans, Pontiac GTO and 4 others.
| Displacement | 326 ci / 5.3 L |
|---|---|
| Bore | 3.811" |
| Stroke | 3.563" |
| Cylinders | 8 |
| Compression ratio | 8.6:1 |
| Bore/stroke ratio | 1.07 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 250 hp |
| Bore/stroke character | 1.070 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,563 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 40.8 ci |
| Static compression | 8.6:1 — low by modern standards, generally happy on regular pump fuel |
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