chiders

Disclaimer: I've never done any engine work in my life--only a few oil changes on my 3.6L. And while it's probably not recommended, I was able to do the entire project myself. Professionally, I'm and enterprise technology sales guy, so definitely out of my wheelhouse. That stated, this post is intended for newbs, not the seasoned weekend mechanic.

Why? The day I purchased my JKU in 2015, I often found myself longing for V8 power--daydreams of dune-blasting, trail hogging, interstate blazing--HEMI fortitude. Especially after loading up my JKU with all that metal armor. But it was new and the Pentastar worked perfectly fine. So I patiently waited 8 years (~80k miles) to transform it into the monster I've always wanted.




1. Getting Started & Considerations

Garage. Having a clean, spacious, well-lit garage made my project much easier. I started with a pretty modest toolset, but over the course of the project, my garage matured (and shrunk), with the addition of bigger items and hand tools. You can probably make it work anywhere, but definitely consider the space you have.

Tools. I already owned a decent socket set along with some other typical suburban dad basics. Necessities that I purchased for the project (not exhaustive list): Engine hoist (cherry picker), engine stand, wheel caddies (to slide the vehicle around), digital torque wrench, shop lights, OBD scanner (bluedriver worked great).

Kit (or Shop?)

Initially, I considered a conversion shop as an option (AMW, Rubitrux, etc.), but they all started around $50k-$60k and had long lead times (3-4 months). I was less concerned about the cost (I'm not rich), but was really anxious to get the project going, so ruled out the shop. I wasn't inclined to program an ECU, build custom a wiring harness, brackets, exhaust, etc., so I determined I'd go with a kit. I researched all of the well known kits (JSS, Dakota Customs, Nuthouse, Hotwire, etc.) and ultimately chose Dakota Customs.

Note: As others have mentioned, Todd at JSS was an extremely helpful resource. In fact, my plan was to buy their kit, but some of the key components were on backorder (e.g. wiring harness--a must have for me). DC was on the higher end of the cost spectrum, but they had everything in stock and shipped within a few days. All that said, I'm extremely happy with the DC kit results (more on that later).

Engine. Do your due diligence and research the engine, thoroughly. I initially purchased a used 392 on ebay listed as "rebuilt" with 0 miles, which ended up being a complete nightmare. The seller appeared to be very reputable, not suspicious...legit. But the listing was seriously inaccurate (either inadvertent or severely sloppy) and was missing multiple items that cost me dearly, timing-wise: Intake manifold damaged with metal chunks (fortunately I discovered before installing). Missing power steering pump, missing engine wiring harness, missing crankshaft bushing, missing flywheel bolts, incorrect alternator. The seller credited me for a few of these, and I also ended up paying out of pocket for a few.

Transmission. My JKU came stock with a NAG1 (5-speed auto), but I was intrigued by 8-speed-butter-smooth-shifting upgrade stories. In my mind, I was convinced that I would regret not upgrading. But I couldn't justify tossing the NAG1--I take good care of my vehicles service-wise, and it helped keep costs lower. After 5 months of driving, I'm still very happy with the NAG1. In fact, I kind of prefer the unsubtle shift transitions, it seems to emphasize the HEMI brawn. What I don't know is how much I'd be saving with 8-speed fuel economy.

Parts. MOPAR is great if you know exactly what you need, you can easily reference parts by model or year. But not so great for searching by configuration/application. Part drawings and diagrams can be pretty sad too. While there are great resources out there, I found that there was still a uniqueness in my build. Sensors, in particular, can be painful.

2. Firing Up Engine #1: Darkness

Upon getting all "correct" parts, I was finally able to install the engine, but I knew something was off the first time I fired it up. It definitely idled weird, the throttle hesitated, and lots of persisting error codes (timing/camshaft/crankshaft). I attempted ~10 different sensors to kill the correct error codes with no success. DC also sent me a new ECU, to rule out a possible programming issue, but made no difference. Dark thoughts were starting to take over...

Light in the tunnel. After a month of f*cking around with the engine, ebay approved the return (overall brutal process and the seller fought every step of the way). That same day my return was approved, I ordered a new crate 392 from MOPAR. Good news: I'd already done all of the prep work for the chassis/body/kit. Bad News: Crate engines come bare bones, so I needed go order more stuff.

3. Firing Up Engine #2: Euphoria
It took about 3-4 days total to get the new engine installed and everything torqued down. I fired it up and...WOW! JKU HEMI BABY! The hardest part was finally done...mostly.

4. Emissions, Adjustments & Break-in

My next step was addressing codes and emissions. My DC kit included a pre-programmed ECU, and I actually had no error codes on my dash, and it was growling beautifully after 20-30 miles. Great! Done! Well not so fast...

Coincidentally, my plates expired over the course of the project, so I headed to the DMV to renew my plates...FAIL! The report indicated it was the O2/catalytic. I searched my guts out trying to figure out if it was due to a lack of break-in period, a bad sensor, etc. So I extended my plates and drive ~100 miles to clear the required ECU sensor tests. Then back down to the DMV...FAIL. I swapped out a few different combinations of sensors (different years/models). FAIL again. Now I was just pissed.

My next move was reaching out to DC, who reiterated that they've done this thousands of times, and have never had issues with O2 tests. But they agreed to try another ECU. Oddly, that ECU triggered some dash codes, the idle was off, and stalled. Now I was really baffled. So I swapped the previous ECU back and reset my thoughts.

My last resort was the DMV, which said the error was due to the ECU program lacking O2 sensor activation. I dumped the ECU binary and forwarded it to DC, and while they were emphatically insistent that this was not related to their programming, they sent me yet another ECU. Installed it, drove ~50 miles, then back to the DMV...PASS.

Other Considerations

Weight. The 392 weighs ~300lbs more than the 3.6L, so I decided to offset with an aluminum front bumper (~$800) and fiberglass hood (~$500).

Fuel. MPG is bad, but not unexpected, ranging around 12-14MPG.

Fan. My stock Pentastar fan was now basically 0% or 100%, which was loud during low idling, so upgraded the controller with an RPM Extreme PWM for ~$400.

Helpful Resources

• Instructions/Guides: Compiled a few difference BOM/instruction resources here.
• Videos: JK Gear & Gadgets / gostlyrich / JKU 392 ADVENTURE / Jeep Speed Shop / Sand Shark
• Torque specs: project-jk / 2016_6.4_torque_specs / dodge-specs / Summit / dodge-specs

GOOD LUCK!

PS. If you're in the market for a very well-maintained 3.6L Pentastar with 80k miles on it, I have one boxed up with OEM accessories:

resharp001

That is a great post! Thank you so much for taking the time to join and post it up. I plan to keep my jeep forever and one day this might be the end result, should the 3.6L ever die on me and the body still has life.