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
258
Primer : Are you lost in a maze of vacuum hoses? Are
having problems passing your state smog check? This article
covers everything you need to know to fix and understand your
258.
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.
Computer
By-Pass: John Nutter's alternative ignition modification
for the 4.2L engine.
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