See other engines in this family
The same engine also has a main page: Chevrolet LD4.
GMC LD4 specs: 250 ci (4.1L) 6-cylinder, 3.875 x 3.53 in (98.4 x 89.7 mm) bore and stroke. Rated 100-105 hp, 1974–1978. Used in the GMC Jimmy. OHV.
The GMC Chevy Straight-6 (194/230/250/292) (LD4) is oversquare — the 3.875" bore exceeds the 3.53" stroke by 9.8% — a layout that favors airflow and RPM over leverage at the crank. The 3.53" stroke puts mean piston speed at 4,000 ft/min around 6,800 RPM, which is where a production bottom end is generally considered at its limit. Each of the 6 cylinders displaces 41.7 ci (683 cc).
It is one of 10 engines in the Chevy Straight-6 (194/230/250/292) family, sitting between the 194 ci and 292 ci members. 4 factory variants share these dimensions, rated from 100 to 105 hp across 1974–1978.
| Displacement | 250 ci / 4.1 L |
|---|---|
| Bore | 3.875" |
| Stroke | 3.53" |
| Cylinders | 6 |
| Configuration | I6 |
| Bore/stroke ratio | 1.098 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 100–105 hp |
| Years | 1974–1978 |
| Bore/stroke character | 1.098 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,530 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 41.7 ci |
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 |
|---|---|---|
| 1974 | 100 hp | LD4 |
| 1975 | 105 hp | LD4 |
| 1976 | 100 hp | LD4 |
| 1978 | 100 hp | LD4 |