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Pontiac L27 specs: 231 ci (3.8L) 6-cylinder, 3.799 x 3.402 in (96.5 x 86.4 mm) bore and stroke, 9:1 compression. Rated 170 hp. Rod ratio and piston speed.
The Pontiac GM 3800 V6 (L27) is oversquare — the 3.7992" bore exceeds the 3.4016" stroke by 11.7% — a layout that favors airflow and RPM over leverage at the crank. The 3.4016" stroke does not reach 4,000 ft/min of mean piston speed until about 7,050 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 38.5 ci (631 cc).
9:1 on iron heads is low by modern standards and generally happy on regular pump fuel.
It is one of 3 engines in the GM 3800 V6 family, all of them 231 ci — the differences between them are in compression, heads and rating, not displacement. 2 factory variants share these dimensions, rated at 170 hp. Factory fitments include the Pontiac Bonneville, Pontiac Grand Prix, Pontiac Firebird and 2 others.
| Displacement | 231 ci / 3.8 L |
|---|---|
| Bore | 3.7992" |
| Stroke | 3.4016" |
| Cylinders | 6 |
| Compression ratio | 9:1 |
| Bore/stroke ratio | 1.117 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 170 hp |
| Bore/stroke character | 1.117 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,402 ft/min — conservative for a street engine |
| Displacement per cylinder | 38.5 ci |
| Static compression | 9:1 — 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 |
|---|---|---|
| — | 170 hp | L27 |
| — | 170 hp | L27 |