If you've ever been disappointed by the horsepower figures coming from your Jeep Wrangler JK, whether it has the 3.8-liter or the 3.6-liter V-6, and you've considered an LS swap, you're not alone. When a Jeep is fitted with heavy aftermarket equipment or loaded down with gear, the engine can easily become overtaxed. Although power-adding solutions do exist, sometimes it can be difficult to overcome the demands of off-road equipment.
Performing an LS swap, or any V-8 swap for that matter, can be a remedy for an underpowered Wrangler. We opted to replace the Pentastar 3.6-liter V-6 in our 2016 Jeep Wrangler Unlimited Rubicon with the all-aluminum LH8 5.3-liter LS engine found in the H3 Hummer. The upgrade should give the Jeep enough power—300 hp and 325 lb-ft of torque—to easily handle larger tires and our increased payload.
Related: 3 of the Best Jeep V-8 Engine Swaps
Bruiser Conversions, an industry leader in fully integrated engine conversions for the Wrangler platform, helped with the swap, and we documented the process. Follow along for some highlights and pro tips from our Jeep JK LS V-8 swap.
To start, we made sure to clear any engine codes that may have been stored in the ECU. This is a mandatory step prior to removing the stock PCM and battery system.
Next we drained the engine oil, power steering fluid, and coolant. We also had a mobile A/C service come to the shop and evacuate our system (you should never evacuate the system into the atmosphere) and store it for reuse later. Keep in mind the type of refrigerant your system uses. It'll likely be using R134a, but in our case it was R1234yf. If you're unlucky enough to have R1234yf, be prepared for how expensive that refrigerant is; a fill can cost upwards of $350.
In our case, the removal of the engine also included the removal of the supercharger system. The system was great while it lasted but can definitely benefit from a tune based on how your vehicle is set up.
We also removed the core support and radiator. Bruiser Conversions can utilize the stock radiator, so you'll want to hang onto it. In our case, we got ourselves a shiny new Mishimoto replacement.
Next we carefully disconnected the engine harness from its various connection points. The rule of thumb here is to work counterclockwise. The harness from the firewall will have various branches tapped into it, which may be zip-tied to the frame. It is not advisable to cut anything unless you absolutely know what you are doing. We took great care with our totally integrated power module (TIPM) because we'll be reusing it.
If you're like us and are running a PSC Motorsports power steering pump, you'll want to remove that and set it aside. If it's one of the newer pumps you may be able to use it with the new engine. Check with PSC on which model you have. PSC makes a specific kit for LS swaps. Pro tip: Make sure to check all your parts with PSC and obtain what you need in advance to avoid major delays in your swap.
Make sure to remove the main engine harness connections to the stock PCM. Depending on your arrangement with Bruiser Conversions, this may be a "core" item that would have to be returned to the company. Note that we will be tapping into the harness to connect the interface with the Bruiser Conversions PCM.
We disconnected all the EVAP lines, radiator hoses, and fuel lines. Take your time and be methodical as there is an abundance of clips and plastic connections you do not want to break. In addition, it's easier to just cut the two radiator hoses that connect to the firewall since Bruiser supplies new ones. Finally, if and when you encounter these clips, take your time; they usually connect hard lines to fittings, and they love to go flying.
Another item that we removed and tossed was the EVAP pump, but we hung onto our EVAP solenoid and fittings.
Next up, we removed the driveshafts and transfer case. It's highly recommended to enlist the assistance of a couple of people to help remove the T-case as it needs to be rocked out of its connection with the transmission. This is a good time to clean, reseal, and/or rebuild your T-case. Also, in regard to the driveshafts, you'll likely need to get a shorter rear 'shaft and longer front 'shaft to complete the install.
We'll be ditching our old six-speed manual transmission and replacing it with a new Tremec TR-4050 five-speed from McLeod Racing/Silver Sport Transmissions.
Also, prior to the removal of the engine, we disconnected the exhaust from the headers rearward, as Bruiser supplies a new Y-pipe and catalytic converters. Note that the new exhaust will potentially have to be welded to the new or existing system in a couple of places.
With the engine supported, we unbolted the motor mounts and prepared to remove the engine from the vehicle. Pro tip: If you have a large stinger on your bumper, remove it. We kept ours on because we figured we could work around it since we had a forklift to pull out the engine, but even so we struggled to clear it.
We extracted the engine and transmission as a single unit (it can be removed separately, but we prefer this method).
With the old engine and transmission removed it was time to prep for the new engine and transmission. It was a good time to power wash the engine bay and address any issues that might get in the way. We made sure to plug all the holes to prevent water from getting in where it shouldn't. Overall, the removal is a pretty involved process that goes beyond quickly disconnecting and unbolting. Care must be taken to not damage fittings, connections, and the vehicle itself. The cleaner your work here the better the rest of the swap will be. In case you're wondering about accessories you'll be able to keep, in our case we had a dual sPOD unit as well as a dual battery kit from Genesis Offroad and the new swap will allow us to retain all of those items. In the next installment of the build, we'll dig into the new swap components, so stay tuned.
Care must be taken when measuring the tolerances before mating the transmission to the engine. McLeod/Silver Sport provides instructions on how to make sure everything is within spec. The two measurements ensure there is proper travel between where the throwout bearing and pressure plate engage, as well as ensuring that you are centered between the bellhousing and transmission.
McLeod provides everything needed to install your clutch and flywheel assembly. It was unfortunate to cover up such a great looking part with the bellhousing.
The bellhousing is a specific unit from Advanced Adapters that's designed for mating the Silver Sport Transmissions Tremec TR-4050 to the LS engine.
Once the engine and transmission were mated together, the final accessories were installed onto the engine.
A relocation kit was provided by Silver Sport Transmissions that placed the shifter in the correct position to pass through the transmission tunnel.
Installing the engine/trans was far from a one-man job. You can see the stinger on the front of the Jeep and how that impacted our angle of approach. Never again.
We had a person positioned under the rig to help guide the transmission assembly into its proper place and look out for anything impeding its placement.
In order to fit the transmission high enough, part of the transmission tunnel had to be cut to clear the relocated shifter assembly.
Unforeseen elements came by way of some major modification to both crossmembers as well as the provided transmission mount adapter. Justin from KrashFab had to clearance a large section of the crossmember as well as shorten the mount to place everything back into its stock location since maintaining clearance was a necessity.
Once the engine and transmission were installed, we realized our tolerances were extremely tight, though everything fit. We took great care to not damage anything during the install, including avoiding smashing plugs against the frame.
Due to the addition of our PSC Motorsports power steering system, we needed to install an ICT bracket that relocated our alternator to the bottom of the motor versus the stock top location.
Here you can see how tight the tolerance is against the steering box.
With everything buttoned up we topped off the radiator, filled the engine with Torco oil, and fired up the LS.
Another unique issue we encountered was the fact that the instructions for the hydraulic throwout bearing called for a Wilwood clutch master cylinder. As we hadn't accounted for this, Keith had to modify our line to work with the stock JK unit.
Since the LS is drive-by-wire, we acquired a new gas pedal that would work with the new engine.
The new PCM used with the engine would be located below the brake booster by way of a bracket designed to utilize two of the lower studs for the booster. In order to install it in this location a hole had to be drilled through the firewall. This hole would allow us to run all of the necessary wiring for the secondary OBD-II port that would be installed in the cab.
The only alternators available to us initially came in low-powered 104-amp models. Multiple alternators were tested for fitment before we realized we needed a small-truck-body unit. Luckily, we found one in the form of a Silverado 1500 unit. In the end, AutoTech Engineering (no relation to our install shop) in Riverside, California, had the alternator we really needed—it puts out a whopping 180 amps in a similar small form factor.
As you can see, we were very limited on clearance. As a matter of fact, it was non-existent as this photo of our new high-amp AutoTech Engineering alternator resting up against the steering box shows. We trimmed a tab on the alternator case to create more room.
We cut off the end of the T-case bracket and drilled into the bracket to clear the stud. This got rid of about an inch of material and helped us clear the driveshaft.
The modified T-case bracket has provided us with plenty of clearance and zero issues. Here you can see the driveshaft installed and it clears the T-case shifter bracket.
The exhaust that was on our Wrangler when it was powered by the V-6 came too close to various components in and around the engine.
The team at MagnaFlow got to work and customized an xMOD Series exhaust system that not only clears all components but also sounds amazing. If you need any emissions control devices, MagnaFlow makes EPA- and ARB-compliant catalytic converters.
If this sight makes your stomach turn, this LS V-8 swap may not be for you. This was our Wrangler's recent gas mileage while romping around the lakebed in Johnson Valley, California.
Everything has a price, right? So about now you may be wondering what the price tag is to do an LS V-8 swap on a Wrangler JK. Well, those numbers can vary quite a bit, but here are some approximate costs.
—Written and photographed by Ali Sedaghat