AMC 258 I6¶
The AMC 258 was introduced in 1971 in J-series pickups and Wagoneers and in 1972 in CJs. It continued to be used through 1990 in the Wrangler. It is basically a stroked 232 engine. The great thing about this engine is it reliable, inexpensive, and has horse power and toque peaks at low RPM.
The 258 inline 6 (I6) engine always came from the factory carbureted any many people complain about the Carter BBD carburetor and the maze of emissions vacuum hoses. There are a couple articles below that can help you sort through those hoses and tune the Carter BBD. For a carbureted engine, the 258 with the Carter BBD performs very well off road. The 258 always came with a cast iron block and cylinder head, hydraulic lifters (with non-adjustable rockers), and 7 main bearings.
The 258 used in '87-'90 Wrangler YJs uses a computer controlled Carter BBD. It is very similar to the 258 used in '82-'86 CJs, but performance suffers due to emission controls.
| Attribute | Specification |
|---|---|
| Bore x Stroke | 3.75" x 3.90" |
| Displacement | 258 (4.2L) |
| Compression Ratio | 9.2:1 |
| Horsepower (net) | 112@3200 |
| Torque (net) | 210@2000 |
| Main Bearings | 7 |
| Valve Configuration | OHV |
| Fuel | 2bbl Carter BBD |
The 258 used in '82-'86 CJs used a computer-controlled Carter BBD. The computer controls mixture based on an O2 sensor and other sensors.
| Attribute | Specification |
|---|---|
| Bore x Stroke | 3.75" x 3.90" |
| Displacement | 258 (4.2L) |
| Compression Ratio | 9.2:1 |
| Horsepower (net) | 115@3200 |
| Torque (net) | 210@1800 |
| Main Bearings | 7 |
| Valve Configuration | OHV |
| Fuel | 2bbl Carter BBD |
The 258 used in '79-'81 CJs, some used a 1bbl carb and some used a 2bbl carb.
| Attribute | Specification |
|---|---|
| Bore x Stroke | 3.75" x 3.90" |
| Displacement | 258 (4.2L) |
| Compression Ratio | 8.3:1 |
| Horsepower (net) | 110@3500 |
| Torque (net) | 195@2000 |
| Main Bearings | 7 |
| Valve Configuration | OHV |
| Fuel | 1bbl and 2bbl |
The 258 used in '72-'78 CJs, J-series pickups, and Wagoneers, some used a 1bbl carb and lower compression than later 258s.
| Attribute | Specification |
|---|---|
| Bore x Stroke | 3.75" x 3.90" |
| Displacement | 258 (4.2L) |
| Compression Ratio | 8.0:1 |
| Horsepower (net) | 110@3500 |
| Torque (net) | 195@2000 |
| Main Bearings | 7 |
| Valve Configuration | OHV |
| Fuel | 1bbl |
The 258 was introduced in 1971 as the standard engine in J-series pickups and Wagoneers.
| Attribute | Specification |
|---|---|
| Bore x Stroke | 3.75" x 3.90" |
| Displacement | 258 (4.2L) |
| Compression Ratio | 8.5:1 |
| Horsepower (gross) | 150@3800 |
| Torque (gross) | 240@1800 |
| Main Bearings | 7 |
| Valve Configuration | OHV |
| Fuel | 1bbl Carter or Holley |
