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Jeep JK Semi-Budget Hemi Swap

Posted in How To: Engine on October 6, 2016
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Those craving the torque and character of a third-gen Hemi engine in their JK have numerous options, none of which are going to be that easy on the wallet. It all depends on how much power you want and how fast you want it done. We’ve seen swaps approaching $40,000, and that’s just going to cover the cost of a new engine, the swap kit, and labor. If you’re going to add a lift kit, taller tires, and beef up the driveline to take advantage of that extra power, then prepare to max out the credit card.

Hemi conversions are not new to the Wrangler community, and dozens of shops around the country advertise them. There are basic swaps working with a stock 5.7L Hemi all the way up to a supercharged 6.2L Hellcat engine. Some shops even offer stroked versions of the Hemi up to 7.2L or 440ci.

Dakota Customs of Rapid City, South Dakota, is arguably one of the pioneers in developing Hemi-swap kits for the JK platform, has developed swap kits for all the popular engines, and offers extensive experience in solving any problem associated with putting V-8 engines in Jeep Wranglers. Our challenge to Dakota Customs was to devise a swap strategy that stretched the value of the dollar and still provided the desired Hemi torque and exhaust note. A good place to start is a used engine, whether it’s found online or at a salvage yard. A new 5.7L crate engine from Mopar Performance will run around $5,000. Dakota Customs found this 5.7L Hemi out of a ’11 Durango with 61,000 miles on the odometer for $2,400. It came with all the accessories and front drive. Not bad.

The Dakota Customs swap kit for this engine includes motor mounts, wiring harness, programmed power control module (PCM), hoses, new air box, power steering fluid cooler, and washer fluid relocation bracket, and it usually costs around $7,900. It also gets you a Borla header and exhaust system, but since this project is budget-minded, we asked to delete the exhaust option in favor of stock exhaust manifolds and a trip to the muffler shop to have the new catalytic converters and exhaust system installed. That saved about $1,900. We also used the stock radiator, but many Dakota Customs kits will include a new aluminum radiator with bigger, more powerful engines.

For swaps into ’12-current JK models, the stock transmission will support the power of a 5.7L engine. However, a Hemi bellhousing and torque converter are needed. For this project, the owner found the necessary parts from a ’10 Grand Cherokee and also pulled the oil pan off the 6.1L V-8 engine in that vehicle. A Hemi starter is also needed.

Labor to install the Hemi can vary widely at a qualified 4x4 shop. However, this swap is rather straightforward with no fabricating or welding required. There are tricks that experienced mechanics and hot-rodders can use to simplify a swap, but the procedure is detailed in the instructions. While this swap was done in a shop, it can be performed in a home garage with the proper equipment. Aside from a basic toolset, you’ll need an angle grinder with cut-off wheels, air-saw (or something comparable), and a tubing flare tool that will perform double flares. Of course, an engine hoist will be needed, along with a method of lifting the vehicle to disconnect the driveline and loosen necessary hardware.

Overall this project totaled $9,565 for parts. If you and your buddies can spin the wrenches, that’s a reasonably cost-effective jump in horsepower and exhaust growl from a V-8 that will turn heads on the trail. See how we got it done, and what we learned from the pros about Hemi swaps.

The factory engine in our subject JK was a standard 3.6L 285hp Pentastar V-6 with 260 lb-ft of peak torque.
Seen after the swap, our new 5.7L Hemi offered 360 hp and 390 lb-ft of peak torque. Note how the washer fluid reservoir was moved to the opposite side to make room for the air box. The battery, fuse box, and ABS pump remained in the factory location.
Here's an overview of all the components needed for the swap. On the table are the parts supplied by Dakota Customs, including the ECU, wiring harness, hoses, oil cooler for the power steering, and air box. The installer needs to supply the Hemi engine, accessory drive, flexplate, and bellhousing. The automatic transmission behind ’12-current versions of the V-6 can be adapted to the V-8 with the proper bellhousing. The ’07-’11 JK has a one-piece tranny/bellhousing, so it can't be mated to a Hemi, and that transmission wouldn't support Hemi torque levels anyway.
The factory six-speed manual behind a 3.8L or 3.6L V-6 will not mate with the Hemi, nor will it stand up to the torque. If a manual transmission is desired, the units found behind the 4.7L V-8s in the Dakota are a good choice. It's the same length as the automatic, and one of the best flywheel/clutch assemblies is from a ’08 Ram 2500 with a 5.7L Hemi.
This swap started with a 5.7L Hemi found in a salvage yard for $2,200. The block was painted Hemi Orange and fit with an oil pan from a 6.1L V-8 Grand Cherokee. The bellhousing is also from a 6.1L V-8 Grand Cherokee, so it matches up perfectly and also provides a rear sump location. We went with factory exhaust manifolds, which then required a visit to a muffler shop to mount the catalytic converters and exhaust system. Dakota Custom does offer steel tubular headers and Borla exhaust as part of a kit, but our strategy saved us $1,900.
The stock JK PCM will work only with the 3.6L V-6 engine. Dakota Customs will supply and program a PCM to work with the Hemi engine selected for the swap. If a customer wants to the supply a PCM for programming, it must have model number 611AC out of a Challenger. The stock transmission controller can be used only if it comes out of a ’12-current JK, and Dakota Customs must program in the Hemi shift points and torque management calibrations.
The left-side tray (supporting) the ABS, PCM, and washer-fluid reservoir) and the right-side battery tray were removed along with the catalytic converters before the V-6 engine was lifted out.
The usual prep work was needed before the stock V-6 and transmission come out, including removing the front grille and core support, disconnecting all the required electrical and fluid lines, unbolting the transfer case, and removing the drivelines. It’s a good idea to pay careful attention to ground-wires and under-hood harnesses.
Next, we removed the fluid pump and clutch assembly from the stock transmission.
The fluid pump and clutch assembly need to be swapped from the stock bellhousing to the V-8 bellhousing before the transmission was bolted to the bellhousing. It's very important to keep all surfaces clean and not to force any parts into position. Also, do this step in one sitting—don't leave it half-finished overnight.
Not every Hemi will have the correct spacer ring in the rear flange of the crankshaft. If using a ’12-current transmission, the spacer will be needed. Check with Dakota Customs to ensure compatibility with the donor and engine and transmissions.
With the transmission bolted to the Hemi, the fuel lines, vent tubes, transmission cooler lines, and dipstick were then installed.
Brackets for the vent tubes were taken off the stock transmission and used again, just like the fuel lines.
In order to clear the left-side exhaust the steering shaft was relocated by enlarging the hole on the firewall. The kit-supplied offset mounting bracket came in hand here.
Another view of the steering shaft relocation helps you see exactly what work is needed.
Some cutting on the vehicle, such as trimming the upper control-arm mounting bracket, was required. Also, as the Hemi provides enough vacuum to properly operate the power brakes, the auxiliary vacuum pump was be removed and the mounting bracket cut off.
The new washer reservoir tray and air box were painted before installation.
The engine and transmission were lowered into the engine bay. It's best to install the engine wiring harness before dropping in the engine. As with any engine installation, don't tighten up all the bolts until all other components are in place.
It was easier to position the engine and start hooking up some of the connections, such as the heater hoses, with the intake manifold off. Other lines were also connected, like the power steering. The kit includes a new pressure side hose. The return line was cut down to reroute fluid to the new cooler.
An edge off the mounting boss located on the AC compressor needed to be chamfered to clear the steering box. The kit also included a special flathead Allen bolt (arrow) for additional clearance in that area.
This stage of the install was a good time to get the intake manifold bolted up and hook up the fuel lines. The battery box was then installed to facilitate wiring on the passenger side. The throttle body, which was taken off for painting, was also re-installed at this time.
The tray supporting the washer fluid had to be sectioned. Only the left side was retained to support the ABS system in the factory location. The washer fluid reservoir was relocated to the passenger-side of the engine bay to make room for the air box.
Progress was made on the left side with the installation of the new air inlet, and the ABS was installed using the modified support tray.
A double-flaring tool was required to install the power-steering fluid cooler.
Relocating the washer-fluid reservoir to the right side required extending the fluid hose to the hood-mounted nozzles.
When the radiator and core support were installed, the power-steering fluid cooler (see inset) could be positioned and the lines hooked up. Note the throttle body installation.
Connecting the wiring harness to the PCM and TIPM was mostly a plug-n-play operation. The only soldering required was to extend the wires for the washer fluid pump. Dakota Customs offers separate instructions if you want to install a cruise control.
The only modification to the electrical system was extending the wiring to the washer-fluid pump after it was relocated to the right side.
The aluminum air box and washer reservoir support supplied in the kit were painted black before being installed. Note the routing of the new radiator hoses and the new radiator catch can.
The final steps of the Hemi V-8 swap included the re-installation of the grille and bumper.
This Jeep was taken to a muffler shop for installation of the exhaust system. The stock driveshafts and transfer case connected right up to the new powertrain.


Dakota Customs

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