How to LS Swap a Jeep XJ Cherokee (photos)
The GM LS engine family has proven itself at being reliable, and easy to modify. Stock they overpower the Jeep 4.0, and they can easily make more. If you are going to put one in a Jeep XJ Cherokee, here's a quick rundown of the work ahead.
1. More Power
The Jeep Cherokee XJ of 1984 to 2001 was truly the first modern Jeep, and straddled the border between the old school off-road focused models and the latest 21st century on-road models. They featured a unibody construction for less weight and easier assembly, coil spring suspension all the way around, but retained solid axles front and back. Unfortunately, modern power was not in the cards from AMC/Jeep in the 1980s, and they did the best they could with motors first used in the 1960s, and units borrowed from General Motors. These days swapping in an LS based V8 is a fairly easy way to double the power under the hood.
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2. The Brains
If you are shopping for an XJ to swap a motor into, the later versions have a computer that can be adapted to the GM EFI, or else you need to do some more adapting. If your XJ is pre-1995, you will want to remove the individual ECM and TCM units. You can toss the engine harnesses and ECM and use a standalone, or factory GM computer, but make sure to keep the chassis harnesses and computer. If you have an XJ that is 96 or later, like the one pictured above, you are in luck as you can keep your PCM. The downside of the more modern XJ though is that the GM computer won't talk to the Jeep instrument cluster, so you'll need to build your own from aftermarket gauges.
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3. Engine Mounts and Lift Kit
No, you don't need to lift your XJ to swap in an LS motor, but if you are removing the four cylinder motor, or 2.8 liter V6, you need new springs anyway. The Jeep straight six, and GM LS V8 are similar in weight, so any spring for the 4.0 is fine with the V8. A lift of two inches or more is recommended to allow clearance between the oil pan, exhaust system, and front axle.
You can make your own engine mounts if you are handy with a welder, or you can get some from an aftermarket supplier. Novak Conversions makes a swell set of mounts that bolt in (though a weld reinforcement is recommended), as well as every single part you need for the swap.
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4. Oil Pan and Intake Manifold
You can swap any of the LS based motors into a jeep you want, from the 4.8 liter truck motor, to the 6.2 liter Corvette powerplant. However, you will need to do some mixing and matching of intakes, oil pans and accessory drives to make it all fit in the Jeep.
Oil Pans - An aftermarket pan like the Holley LS retrofit unit will give you the most clearance. Many people have been fine using the Camaro/Firebird or CTS-V unit however. It really depends on how much lift and articulation you have. Be sure to get the correct pump/pickup for the pan.
Intake manifold - If you want to run a stock hood, you must use the Camaro/Corvette intake. Otherwise a cowl induction hood with a few extra inches will clear the truck intake.
Accessory Drive - The Corvette accessory drive is recommended becasue it moves the alternator out of the way of the low Jeep hood.
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5. Cooling System
Once you have drained the coolant from the old radiator, reservoir and hoses, you can pull the radiator and recycle it. The Jeep radiator is inadequate for the LS engine. Also remove the A/C condenser, transmission cooler and just about everything up including the grill and front crossmember. Unfortunately, the low hood height and small grill makes it hard to find a factory LS radiator that fits, so Novak made one. Otherwise, find any generic LS aluminum radiator that is small enough to fix in the engine bay.
Also, the stock A/C compressor location is not going to fit, so you will either need to eliminate air conditioning, or get a relocation kit.
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6. Exhaust Manifolds
If you are using the Novak motor mounts, it is recommended you order their headers as well. If you are creating your own mounts, or using universal weld in units, you may be able to get away the using factory F-body (Camaro/Firebird) manifolds. The one pictured above is actually the factory C6 Corvette manifold (on a Wrangler), which is quite compact. Many people have used block hugger style center dump universal headers with good results as well.
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7. Transmission
Yes, that picture is a TJ not an XJ, but it is a good example of the powertrain packaging. Face it, the transmission used in the XJ are not the great, especially the early ones. The good thing about the LS is that almost any GM transmission will bolt up to it, and almost any transfer case can be adapted. Again, Novak Conversions has an excellent run down of what works and what doesn't, but the short answer is to try to get a matched motor/transmission out of a parts car. Then just worry about adapting your transfer case to it.
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8. Throttle and Gauges
Once you have all that in, you are on the home stretch. You can now drop in and mount the LS engine. You can and even should, reuse the XJ fuel pump if it is in good working condition and originally had EFI. This will make it easier to replace in the future and it holds plenty more PSI than what the LS calls upon. The throttle linkage cable can be connected, unless your LS is a later model with throttle by wire, which means either swapping to the earlier throttle body, or buying a GM electronic accelerator pedal unit.
A neat project, if you don't want to order up a box of aftermarket gauges, is to adapt the instrument panel from a GM truck, Camaro, or Corvette. Look around the junk yards and eBay for the various styles used in LS powered vehicles. Don't forget, the Hummer H3 and many other trucks have a rectangular gauge package taht should be easy to adapt. You may have to change out the fuel tank sending unit for a GM one that matches the gauge.
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9. Wrapping it up
A note for the A/C if you choose to retain it. If you aren't going to use a relocation kit for the compressor, you will have some cutting and welding to do to the frame to make it fit as is. You should have room on the passenger side for the compressor. There are several good write ups online detailing all of the little issues that may come up, like this one from LS1Tech.
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For help with service and maintenance of your Jeep, check out the how to section of JK-Forum.com