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 |