Performance Upgrades for a Jeep 4.0

by Michael Butler

Between 1987 and 2006, Jeep used a 4.0-liter, inline-6 engine as its standard engine. Originally, the engine was designed by the American Motor Company, but it was later refined by Chrysler. If you want to increase the performance of this engine, you can make several modifications.

Air Intake Conversion

The Jeep's air intake port is located beneath the headlamp on the driver's side. If you take your Jeep off-roading in deep water, it is possible that water can get into the engine. You can help alleviate this problem by using a PVC pipe and high quality air filter to make a different air intake port.

Heavy Flywheel

When the Jeep's engine is under stress, such as when you climb a steep incline, the clutch disk can shatter or the engine may shut off suddenly. This can be fixed by adding weighted inertia rings to the back of the flywheel. This does make the engine work harder to accelerate, but makes it easier to operate on inclines.


You can add a supercharger to the Jeep 4.0-liter engine. A supercharger is an air compressor that will use forced induction to get more air into the engine. This will greatly increase the amount of work that the engine is capable of doing, which increases the power. Many different superchargers are available for purchase and they can be expensive, costing between $2,500 and $7,000 or more.

Increase the Stroke

Another way to increase the amount of air into the engine is to increase the stroke. The more air that goes into an engine in one complete cycle, the more work the engine is capable of performing. The total air in one cycle is referred to as displacement. When you increase the stroke, you increase the displacement. This can add a significant power upgrade to the engine.

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