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 emmissions 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 simlar to the 258 used in '82-'86 CJs,
but performance suffers due to emmission controls.
| AMC 258 I6 |
|---|
| 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 controled Carter BBD. The
computer controls mixture based on an O2 sensor and other sensors.
| AMC 258 I6 |
|---|
| 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.
| AMC 258 I6 |
|---|
| 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.
| AMC 258 I6 |
|---|
| 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.
| AMC 258 I6 |
|---|
| 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 |
Other Information
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Learning to Love
Your 258: An easy fix for the most common idle problems with the
258(4.2L) engine used in Wranglers(YJ) and CJs.
|
Contributors
Some photos courtesy Rick Boiros.
