See other engines in this family
Pontiac 138ci (1989) · 150 hp specs: 138 ci (2.3L) 4-cylinder, 3.625 x 3.35 in (92.1 x 85.1 mm) bore and stroke, 11:1 compression. Rated 150 hp, 1989. OHC.
The Pontiac 138ci (1989) · 150 hp is oversquare — the 3.625" bore exceeds the 3.35" stroke by 8.2% — a layout that favors airflow and RPM over leverage at the crank. The 3.35" stroke does not reach 4,000 ft/min of mean piston speed until about 7,150 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. A rod ratio of 1.734 is in the range most production engines fall in. Each of the 4 cylinders displaces 34.5 ci (565 cc).
11:1 on iron heads is high enough that pump premium or better is normally required, and iron holds heat, so it is the less forgiving side of that line.
It is one of 5 engines in the Pontiac 138ci family, all of them 138 ci — the differences between them are in compression, heads and rating, not displacement.
| Displacement | 138 ci / 2.3 L |
|---|---|
| Bore | 3.625" |
| Stroke | 3.35" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 11:1 |
| Rod length | 5.81" |
| Rod ratio | 1.734 |
| Bore/stroke ratio | 1.082 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHC |
| Fuel type | gas |
| Advertised HP | 150 hp |
| Years | 1989 |
| Bore/stroke character | 1.082 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,350 ft/min — conservative for a street engine |
| Rod ratio | 1.734 — moderate — the range most production V8s fall in |
| Displacement per cylinder | 34.5 ci |
| Static compression | 11:1 — high enough that pump premium or better is normally required |
Each link opens the calculator with this engine's specs already filled in.