Home Page
  Photo Album
  Product Reviews
  Tech Section
  Jeep Central
  Readers Rigs
  4x4 Club Links
  Links Directory
  4x4 Vendors
  Cool Products
  Shop for Stuff
  Centralia PA
  Computer Help
  Contact
  Search
  Site Index
  Project CJ-7
   
 
Jeep Project CJ-7

An ongoing Budgeted Rebuild/Build up of a Rock Crawling Machine.

Jeep Central
From Jeep History to Tech Specs and Projects.  This section is all about Jeeps.
Jeep Technical Info
Engines
Transmissions
Transfercases
Axles
Engine Swaps

 

ATV World
ATV Clubs
ATV Tire FAQs
ATV Tire Mounting
Cool ATV Products
LiteFoot Track Sys
ATV Lift Installs
Quad Tire Reviews
ATV Laws By State
ATV Repair
ATV Manuals

Offroaders Guide to Gearing up for Offroad
From Basic Equipment to Well Equipped.  An extensive list guide to help you prepare your vehicle for the offroad.


Trailering Safety and Trailer Hitch Information


Off-Road Truck Driving Techniques and Safety

25 Top To Do Tips Before Going Offroad

  
Installing 23,000 Volt Offroad Lights

What are HID Lights?

Onboard Air
Converting a York
AC Compressor
to Pump Air

Warn 9500i Winch Installation
 

HEI Ignition
Installation & Review

  

Troubled
Computer?

Got Pop-ups
Spyware & Viruses?
Offroaders.com feels your pain. Let our Geeks help you...
RalphtheGeek.com


Jeep Dana 300 TeraLow - 4:1 Gearset for the Dana 300 Transfer Case

Teraflex Tera Low 20 for the Dana 20 Installation

Tera Low 20
for the Dana 20

 

Warn X8000i
Winch Installation

 

From the
Department of Cheap   Tricks and Useful Tips

  
Ultra-Cool Hand Throttle for Free!

Jeep V8 Swap Tips

The Exploding Clutch

Radiator Protection using 6 bucks worth of material

Cracked Under Pressure - Fixing a smashed fingernail

A Cheap, effective alternative to undercoating

Home-built Saginaw Gearbox Brace for the cost of lunch!

Ammo Box Storage - Mounting Them for Quick Disconnect

Home-built Serious Skid-Plate protection for the Oil Pan for under 20 bucks!

 

 

 

 

Main >> Engine >> Factory >> AMC 258 I6
  
 


  

AMC 258
Photos by Kirk Beasley.

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; some background about the AMC inline 6s (I6s) is given in the article about the 232. The great thing about this engine is it reliable, inexpensive, and has horse power and torque peaks at low RPM.

The 258 has a cast iron block and cylinder head, hydraulic lifters (with non-adjustable rockers), 7 main bearings, and cast iron crankshaft and rods. The 258 I6 engine was always carbureted from the factory. The 1-barrel engines came with the Carter YF carburetor, and the 2-barrel engines came with the Carter BBD. Many people complain about the Carter BBD carburetor and the maze of emissions vacuum hoses. There are a couple of 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.

There are two generations of 258 engines. The first generation was introduced in 1971. This earlier engine has cast iron intake and exhaust manifolds with the two manifolds bolted together by 4 bolts and a gasket between. In 1981, AMC revised the 258 for lighter weight. A new block casting and fewer crankshaft counterweights were used. A new smoother exhaust manifold and aluminum intake manifold were introduced. V-belts were replaced with a serpentine belt, and a new lightweight plastic valve cover was fitted. Although these two generations have the same bellhousing and motormount attachments, and are mostly the same internally, the differences must be kept in mind when choosing used replacement parts.

The 258 can be identified by the 4th character of the engine build date code ("A", "B", "C" or "M"), stamped into the engine block below and between the number 2 and 3 spark plugs. An engine stamped with "B" is an early 258 with a 7.6:1 compression ratio. "A" and "B" are engines with 1-barrel carburetors, while "C" and "M" are 2-barrel. "M" originated in Mexico. Other codes ("E", "F", "K" and "L") are 232 engines.

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.

 

The 4.0 L (3956 cc) straight-6 was an evolution of the 258 and 150 and appeared in 1987. It had the same 3.88 (98.4 mm) bore as the 150 with a longer 3.41 in (86.7 mm) stroke. The 4.0 has been discontinued at the end of the 2006 model year as the Jeep Wrangler will instead get Chrysler's 3.8 L OHV V6. This is at the same time other manufacturers are introducing new I-6 engines.

The first 4.0 engines in 1987 had RENIX (Renault/Bendix) engine control systems, which were quite advanced for their time, but are now handicapped because there are very few scan tools which can be "plugged in" to a RENIX system for diagnosis. The Renix also used a very advanced engine knocking sensor that allowed the computer to make the appropriate changes to prevent predetonation in each cylinder.

In 1991 Chrysler Corporation, then the owners of the Jeep brand, redesigned the engine control computer and the intake ports; the camshaft profile was also changed. The result was an engine that made 190 hp (142 kW) and 225 ftlbf (305 Nm) of torque.

Small changes were made to the cylinder head for the 1995 model year. In 1996, the engine block was updated, it made use of more webbing cast into the block, and a stud girdle for added rigidity of the crankshaft main bearings.

The cylinder head was again changed in 1998 to a lower flowing, but more emissions friendly, design.

This engine was used in the following vehicles::

1987-2001 Jeep Cherokee
1993-2004 Jeep Grand Cherokee
1987-1990 Jeep Wagoneer
1987-1992 Jeep Comanche
1991-2006 Jeep Wrangler

 

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
 

 

 

Pictures
 


The Jeep 258 straight 6 cylinder engine.
Photo courtesy Rick Boiros.

 


The Jeep 258 straight 6 cylinder engine


AMC 258 Passenger Side.
Photo by Kirk Beasley.


AMC 258 Passenger Side.
Photo by Kirk Beasley.


AMC 258 Front.
Photo by Kirk Beasley.

 

 

All text is available under the terms of the GNU Free Documentation License.
Simple HTML for this page here.

Jeep Wrangler JK
Jeep Wrangler JK Specs
Offroad Tire Info
P-Metric Tire Sizes Conversion to Inches
Tire Terminology
Wheel Terminology
How to Pick the Right
Tires for your Truck
Truck Tire Info
Tires - What Hits What Fits
  
All Terrain  Mud Terrain
Tire Reviews & Info
Mud Terrain MT Tire Reviews
All Terrain AT Tire Reviews
Super Swamper Bogger
Super Swamper SSR
Super Swamper SX
Super Swamper Vortrac
Interco IROK TSL
Super Swamper LTB
Super Swamper TSL
Super Swamper TSL Radial
Super Swamper Narrow
Interco SS-M16 Swamper
Thornbird TSl Radial
Thornbird TSl Bias
Thornbird TSL
Parnelli Jone Dirt Grip
BFGoodrich Krawler
BFGoodrich MT T/A KM
BFGoodrich Mud King XT
BFGoodrich MT T/A KM2
Bridgestone Dueler MT
Cooper Discoverer ST
Cooper Discoverer STT
Cooper Discoverer ST/C
Federal Couragia MT
Firestone Destination AT
Firestone Destination MT
General Grabber MT
General Grabber AT2
Green Diamond Icelander
Ground Hawg Mud Tire
Hankook Dynapro MT
Hankook Dynamic MT RT01
Hercules Terra Trac MT
Hercules Trail Digger MT
Kelly-Springfield Safari DTR
Kelly-Springfield Safari MSR
Kumho Road Venture MT
Kumho Road Venture KL71
Kumho Road Venture AT
Dick Cepek Mud Country
Dick Cepek F-C II
Dick Cepek Fun Country II
Dick Cepek Fun Country Nylon
Dick Cepek Fun Country Kevlar
Mastercraft Courser MT
Mastercraft Courser HTR
Mastercraft Courser HTR Plus
Maxxis BigHorn Radial
Maxxis Creepy Crawler
Maxxis Trepador
Maxxis Buckshot Mudder
Maxxis MA-SW
Maxxis M-8080 Mudzilla
Maxxis MT-754 Buckshot
Maxxis MT-753 Bravo
Maxxis MA-751 Bravo
Maxxis MA-S2 Marauder II
Maxxis MA-S1 Marauder
Maxxis MT-762 BigHorn
Nitto Mud Grappler
Nitto Terra Grappler
Nitto Dura Grappler
Nitto Dune Grappler
Nokian Vatiiva MT
Pit Bull Rocker Extreme
Pit Bull Maddog
Pit Bull Growler
Goodyear Wrangler MT/R
Pro Comp Xterrain
Pro Comp All Terrain
Pro Comp Mud Terrain
Pro Comp Xtreme AT
Pro Comp Xtreme MT
Toyo Open Country AT
Toyo Open Country MT
TrXus Mud Terrain
TrXus STS All Terrain
Michelin LTX A/T?
Michelin LTX AT2 Press
Michelin LTX AT2
Mickey Thompson MTZ
Mickey Thompson MTX
Mickey Thompson Baja Claw Radial
Mickey Thompson Baja Claw Bias
Mickey Thompson Baja Crusher
Mickey Thompson Baja ATZ Radial SLT
Competition Claw
Dunlop Mud Rover
Federal Couragia M/T
Nitto Dura Grappler
Yokohama Geolandar
  
Dick Cepek's 2008 F-250 Super Duty Project Vehicle ? Project CRUSHER
 
Mud Tire Reviews

 

Mud Tire Reviews


Jeep Rubicon Articles and Reviews


Jeep Rubicon Unlimited Articles and Reviews

Offroad Reports


Rausch Creek
Off-Road Park


Wheeling in the Valley of the Ferns

1.jpg (70086 bytes)
Tellico North Carolina


Paragon Adventure Park
Rock Krawl

Thousands more
photos here..?

JEEP CJ
AXLE SWAP

Jeep CJ Axle Swap using
Scout II Dana 44 Axles

Building a Garage?
Need a Garage Plan?