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GMC 287 specs: 287 ci (4.7L) 8-cylinder, 3.75 x 3.28 in (95.3 x 83.3 mm) bore and stroke, 8:1 compression. Rated 180 hp. OHV. Rod ratio and piston speed.
The GMC Pontiac V8 (287) is oversquare — the 3.75" bore exceeds the 3.2799" stroke by 14.3% — a layout that favors airflow and RPM over leverage at the crank. The 3.2799" stroke does not reach 4,000 ft/min of mean piston speed until about 7,300 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 8 cylinders displaces 35.9 ci (588 cc).
8:1 on iron heads is low by modern standards and generally happy on regular pump fuel.
It is one of 9 engines in the Pontiac V8 family, the smallest at 287 ci. Factory fitments include the Pontiac Chieftain, Pontiac Star Chief, Pontiac Catalina.
| Displacement | 287 ci / 4.7 L |
|---|---|
| Bore | 3.75" |
| Stroke | 3.2799" |
| Cylinders | 8 |
| Compression ratio | 8:1 |
| Bore/stroke ratio | 1.143 |
| Piston deck clearance | 0.05" |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 180 hp |
| Bore/stroke character | 1.143 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,280 ft/min — conservative for a street engine |
| Displacement per cylinder | 35.9 ci |
| Static compression | 8:1 — low by modern standards, generally happy on regular pump fuel |
| Intake valve diameter | 1.787" |
|---|---|
| Exhaust valve diameter | 1.406" |
| Chamber volume | 52.9 cc |
| Rocker ratio | 1.5:1 |
| Lifter type | hydraulic |
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