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Pontiac 455 specs: 455 ci (7.5L) 8-cylinder, 4.15 x 4.209 in (105.4 x 106.9 mm) bore and stroke, 8.4:1 compression. Rated 310-335 hp. OHV.
The Pontiac V8 (455) is close to square: 4.1496" bore against 4.2087" stroke, within 1.4%, which splits the difference between a high-revving layout and a torque layout. The 4.2087" stroke puts mean piston speed at 4,000 ft/min around 5,700 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 56.9 ci (932 cc).
8.4:1 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 largest at 455 ci. 2 factory variants share these dimensions, rated from 310 to 335 hp. Factory fitments include the Pontiac Firebird Trans Am, Pontiac GTO, Pontiac Grand Ville and 2 others.
| Displacement | 455 ci / 7.5 L |
|---|---|
| Bore | 4.1496" |
| Stroke | 4.2087" |
| Cylinders | 8 |
| Compression ratio | 8.4:1 |
| Bore/stroke ratio | 0.986 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 310–335 hp |
| Bore/stroke character | 0.986 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 4,209 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 56.9 ci |
| Static compression | 8.4:1 — low by modern standards, generally happy on regular pump fuel |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| — | 310 hp | 455, 455 SD |
| — | 335 hp | 455 |