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Oldsmobile LD9 specs: 146 ci (2.4L) 4-cylinder, 3.543 x 3.701 in (90 x 94 mm) bore and stroke, 9.5:1 compression. Rated 150 hp. Rod ratio and piston speed.
The Oldsmobile Quad 4 (LD9) is close to square: 3.5433" bore against 3.7008" stroke, within 4.3%, which splits the difference between a high-revving layout and a torque layout. The 3.7008" stroke puts mean piston speed at 4,000 ft/min around 6,500 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 36.5 ci (598 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 8 engines in the Quad 4 family, the largest at 146 ci. 2 factory variants share these dimensions, rated at 150 hp. Factory fitments include the Oldsmobile Achieva, Oldsmobile Alero, Oldsmobile Cutlass and 5 others.
| Displacement | 146 ci / 2.4 L |
|---|---|
| Bore | 3.5433" |
| Stroke | 3.7008" |
| Cylinders | 4 |
| Compression ratio | 9.5:1 |
| Bore/stroke ratio | 0.957 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 150 hp |
| Bore/stroke character | 0.957 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,701 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 36.5 ci |
| Static compression | 9.5:1 — in the range that usually runs on pump premium |
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 |
|---|---|---|
| — | 150 hp | LD9 |
| — | 150 hp | LD9 |