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The same engine also has a main page: Pontiac GM 60-Degree V6 9.5:1.
Pontiac LA1 specs: 204 ci (3.4L) 6-cylinder, 3.622 x 3.307 in (92 x 84 mm) bore and stroke, 9.5:1 compression. Rated 185 hp. OHV. Rod ratio and piston speed.
The Pontiac 60 Degree V6 (LA1) is oversquare — the 3.622" bore exceeds the 3.3071" stroke by 9.5% — a layout that favors airflow and RPM over leverage at the crank. The 3.3071" stroke does not reach 4,000 ft/min of mean piston speed until about 7,250 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 34.0 ci (557 cc).
9.5:1 on aluminum heads is in the range that usually runs on pump premium; aluminum sheds heat faster than iron, which makes the same number a little more forgiving.
It is one of 2 engines in the 60 Degree V6 family, all of them 204 ci — the differences between them are in compression, heads and rating, not displacement. Factory fitments include the Pontiac Grand Am, Pontiac Montana, Pontiac Aztek.
| Displacement | 204 ci / 3.4 L |
|---|---|
| Bore | 3.622" |
| Stroke | 3.3071" |
| Cylinders | 6 |
| Compression ratio | 9.5:1 |
| Bore/stroke ratio | 1.095 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 185 hp |
| Bore/stroke character | 1.095 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,307 ft/min — conservative for a street engine |
| Displacement per cylinder | 34.0 ci |
| Static compression | 9.5:1 — in the range that usually runs on pump premium |
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