Originally Posted by JeepDeadPedal
I am new and have recently discovered what all of this Jeep stuff I didn't understand is.
Turns out it is mostly great except for a bit of rust and a terrible lack of power.
The lack of power of the 4.0 is easily solved... just take out your wallet.
There are supercharger, turbocharger upgrades [e.g. Hesco], there are strokers
that run from do it yourself to crate engine 4.7 to Monster Forged 5.0 litre beasts.
Unless it has been replaced already, the stock exhaust manifold sucks. Hopefully the prior owner has replaced it and also hopefully added a catback exhaust that can help a bit.
But, what the 4.0 really has if in even halfway decent shape is low end torque and a flat horsepower curve.
By the time it gets spinning fast enough to do the valve rotation, it will pretty much be putting out as much as it can do.