The 4.0L inline 6 (I6) engine was introduced in the Cherokee in the late
80s and in the YJ in 1991. The cylinder design is based on the changes made to the fuel
injected 2.5L I4 engine. The block and cylinder head are cast iron. It uses 7 main
bearings and hydraulic lifters. The HP and torque gains are substantial over the older
carbureted 258, but the peaks come at higher RPM. The fuel injected engine performs much
better in off-camber, bouncy, and steep situations. It also calibrates better for changes
in altitude. Fuel economy is also improved.
A good way to embarass yourself in front of your Jeeping friends is to
refer to it as a V6. It isn't a V6, it is an inline 6 or I6. The "V" in V6
refers to the configuration of the pistons in the block. The only two V6 engines ever
available from the factory in a Jeep are the 225 "Dauntless" Buick V6 in the
late 60s and early 70s and the 2.8L GM V6 in 80s Cherokees and Comanches. If you are
shopping for a Cherokee or Comanche, make sure you get the 4.0L and not the 2.8L engine,
there is a world of difference.
The 4.0L engine used in the Wrangler from '91 until the present.
4.0L I6 |
Bore x Stroke |
3.88" x 3.41" |
Displacement |
242 (4.0L) |
Compression Ratio |
8.8:1 |
Horsepower (net) |
180@4750 |
Torque (net) |
220@4000 |
Main Bearings |
7 |
Valve Configuration |
OHV |
Fuel |
MPI |
The 4.0L I6 that is used in the XJ and ZJ is rated slightly higher than
the YJ and TJ 4.0L engine probably due to a different exhaust system.
4.0L I6 |
Bore x Stroke |
3.88" x 3.41" |
Displacement |
242 (4.0L) |
Compression Ratio |
8.8:1 |
Horsepower (net) |
185@4750 |
Torque (net) |
220@4000 |
Main Bearings |
7 |
Valve Configuration |
OHV |
Fuel |
MPI |