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Mdmike's mall-tastic Hemi powered LJ

mdmike

Red Skull Member
Joined
May 19, 2020
Member Number
195
Messages
221
Loc
Maryland
I figured since it's so easy to upload pics now, I would toss up a mini build thread on my mall-crawler/daily driver LJ. I know a Hemi swap in a TJ/LJ isn't exactly "hardcore" tech (especially for a Jeep like mine), but as I was researching this project, there were quite a few questions I had that were coming up empty on internet searches. Hopefully this little thread might help someone else in the future.

So, a few years ago, my buddy that owns Appalachian Offroad here in Maryland told me he came across a deal on a high mileage LJ. Since he was already neck deep in his own projects, he agreed to pass the deal on to me. I made him an offer he couldn't refuse, and a 269,000 mile 4.0/6 speed LJ showed up in my driveway. It was filthy, a little rusty here and there, but still ran really well for having nearly 300k.
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I did the usual lift/regear/rims/tires and put another 10 thousand or so miles on it knowing I should be keeping an eye out for a low mileage 6 cylinder to replace the tired 4.0. I also managed to scoop up a hard top in the mean time, which I was really excited about.

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Fast forward to that winter and I get a call from my Sister telling me a guy slid through an intersection in an ice storm and hit her Grand Cherokee, totaling it. Thankfully she was ok, but the Jeep took a pretty good hit. The gears in my head started turning, 1 thing led to another, and I bought her Grand back from the insurance company. Her Jeep had just turned 100k miles and I know her and my BIL had taken good care of it throughout its life. The damage was mainly the front passenger fender and core support, and it still ran and drove.

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On to the wrenching:

Here is where the Hemi started life:

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I was surprised at how much of a pain in the ass it was to extract this thing!

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Engine and transmission out and strapped to the table.
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I parked the new drivetrain next to the Jeep hoping nature would take its course and it would just hop in there, but sadly that wasn't the case.

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At this point it was the LJ's turn to go under the knife

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The parts pile just kept growing.

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So, this is the most important part I needed at this point:
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That is the under hood engine wiring harness and fuse box from the LJ. Before I started this project I called a couple of the reputable Hemi swap specialists to figure out exactly what I was going to need to get the wiring harness squared away. The 1st place I called told me I needed to sell the Grand Cherokee engine and buy a truck motor instead :rolleyes: My next call to Chris at Hotwire Auto was far more productive. He basically told me to box up this harness, send it to him, and it a few weeks an all new harness would show up that would be plug and play.

Edit to add: the other necessary component of the wiring harness is a 2005 Dodge Ram Hemi truck ecu. I got mine off of ebay for less than $100.

So, I boxed everything up and shipped it off and that is when the clock started ticking. At the time, I think Hotwire's lead time was about 3 weeks to get the harness done, so I was on a mission to get the new drivetrain installed.
 
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First up was getting the new drivetrain in the Jeep. The go-to for Hemi swap motor mounts in a TJ/LJ is Advanced Adapters and they make life VERY easy. First things first, the stock 6 cylinder mounts have to go

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AA supplies you with a little fixture to get the mounts exactly where they need to be. You pop your brake line bracket out of the frame and use the existing hole for their fixture. Then, you butt the new Hemi mount up to it, and weld it on. Super easy.

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For the transmission mount, I used a part from Teraflex. This allows the 545rfe trans to mount to a skid plate in the stock position. It is their part# 4947183 https://www.amazon.com/TeraFlex-4947...1195174&sr=8-1

What I didn't realize at the time, is that the AA motor mounts and the Teraflex transmission mount locate the drivetrain a few inches taller than the stock mounts. I ended up with a Rough Country "belly up" skid plate and still had to put 1" spacers between the mount and the skid plate.


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So here is a little bit of tech for the thread. The tail housing on the Grand Cherokee has a different bolt pattern for the transfer case. Luckily there is a Mopar part that solves the problem. It is part# 52107719AC. You will also need 2 seals as well, part# 4799090 and part# 501902ab. I got the tail housing from ebay for less than $100.
 
At this point, the drivetrain is in and I started going after each "system" individually.

The first thing that gave me a hard time was the steering. The Grand Cherokee uses a hydraulic cooling fan that is run off of the power steering pump. Because of this, the pressure line is a bigger diameter than the stock line on LJ. I had read about other guys getting custom lines made, but I was trying my best to use off the shelf parts. My first attempt was a truck pump with the integrated reservoir, but that didn't even come close to fitting properly. After some digging, I found that the power steering pump on the Hemi Dodge Chargers mounted to the engine perfectly, but used the smaller diameter hoses that matched the LJ. I was able to creatively re-route the stock pressure line from the LJ and it bolted right up to the box. For a reservoir, I bought the factory piece from a Charger and made a bracket to mount it to the driver's side fender. I was even able to reuse the stock return line from the box to the reservoir, and a line scavenged from the Grand Cherokee to go from the reservoir back to the pump. Unfortunately I don't have any pics of the way I routed the line, but you can see my reservoir location in the bottom/right of this pic:

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Next up was fuel. Luckily, the 05-06 fuel pumps have enough pressure and volume to keep the Hemi happy. I figured since the pump in the Jeep could potentially have 270K miles on it, a replacement was in order. I swear, every time I need to do a fuel pump, the tank is full.

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With the pump done, I had to address getting fuel to the engine. The line from the hard line to the fuel rail on the Grand Cherokee is a bigger diameter than the stock line on the LJ. After some research, I came up with these 2 fittings to get the job done (Vibrant Performance part#'s VPE-16445 and VPE-16881) I had to gently bend the stock hard line to get it where it is, and by flipping the stock flex line from the Grand Cherokee around backwards, it lined up perfectly.

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On to the exhaust. Regardless of which Hemi you're putting in a TJ/LJ, you need to use the stock exhaust manifolds from a Grand Cherokee. I noticed 1 broken manifold bolt when I got the motor out of the Grand, so I decided to replace both manifold gaskets and address any future problems with broken bolts while the engine was out. I bought a replacement manifold bolt kit, tap, and got after it.

Talk about a great time! :laughing:

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If you've ever broken a tap off in a hole, THIS is what victory looks like!!

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With that done, it was time to get the exhaust out the rear of the Jeep. I had read another build thread on a different forum and knew the Grand Cherokee down pipe and cats bolt onto the LJ almost perfectly, but due to the way the front driveshaft on the IFS Grand Cherokee runs to the front dif, it puts the driver's side down pipe right in the way of the LJ front driveshaft. I had never done "custom" exhaust work before, so I figured I'd give it a go. I needed some reaaaally tight bends where the downpipe comes off the manifold, and then down at the converter. I took a piece of exhaust tubing and cut a bunch of 15 degree bends and started taping/tacking the exhaust together until I got it to fit. Then, at the rear I lobbed the flange off of the Grand Cherokee down pipe and welded the flange from the LJ exhaust to it. This exhaust bolts right up to any aftermarket cat-back system. I'm running Banks cat back on it now and it sounds great. I was expecting it to be really loud, but it is surprisingly quiet.

Not my finest work by any stretch, but it clears everything and doesn't leak. I had been "encouraged" by some friends to throw some exhaust wrap over this part of the pipe, but I own this one 100%. :laughing:

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Cooling was up next.

I found a Hemi swap radiator on ebay from Superior Radiator and decided to go with a new Ford Taurus fan. I built some brackets to hold the fan off of the radiator and bolted everything in together

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I was able to cut and sleeve the stock Grand Cherokee upper hose and it worked out good


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The lower hose got the same cut/sleeve treatment, but I had to use some heat and a big socket to get the diameter of the hose over the radiator inlet


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The radiator came with a bung welded in for a fan thermostat switch, which was really convenient. The wiring harness from Hotwire comes with a powered 12v wire for an electric fan, but the computer does not tell the fan when to come on, unlike an LS swap computer would. I bought a 200* on/185* off fan controller that works well: https://www.amazon.com/American-Volt...1191282&sr=8-2

I also addressed the transmission cooler too. I bought a simple plate style cooler from the local auto parts store, welded some tabs onto the support rods in the grill/in front of the radiator, and mounted it up. I was able to use the stock Grand Cherokee transmission cooler lines all the way up to the grill. I cut them there and used rubber hose up to the cooler. Super easy.
 
There were some other odds and ends that needed done too.

Shifters: I got VERY lucky with this. My buddy that runs the offroad shop had a customer come in and want a manual trans swapped into his automatic LJ. The stock automatic shifter and shift cable work perfectly with the 545rfe.

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The transfer case shifter wasn't quite as easy. I tried every which way to get the stock mechanical linkage to work, but failed. I ended up buying a cable shifter setup and it made life a lot easier. https://www.extremeterrain.com/stein...r-9706-tj.html


The Hemi is a "drive by wire" setup. Luckily, the go-to pedal for the install is the Grand Cherokee pedal assembly. Teraflex makes a bracket that makes it a bolt in deal. Part# 4877480

The other thing that needed addressed was the steering shaft. The Advance Adapters driver's side engine mount comes with a bracket welded to it to accommodate a stock 4 cylinder TJ steering shaft bracket. This bracket keeps the steering shaft out of the exhaust. I got a used one from a junk steering shaft my buddy had laying around.



With everything working mechanically, it was time to make things look pretty so the drivetrain came out 1 more time.

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Cleanup and painting done, and the drivetrain went back in for the last time
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The day finally came and this big box of awesome showed up

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The harness from Hotwire is simply a work of art. They start with a brand new Mopar harness and everything fits perfectly. The harness lays on the engine perfect and everything lands right where its supposed to. Yes, it is expensive, but you realize its worth every penny once you put your hands on it. The only other wiring you need to do yourself is the charging wire for the alternator to the battery and the battery to the starter. I was able to reuse the wiring from the Grand Cherokee and it worked out well.

Initial startup was the most anticlimactic event. I hooked up the battery, hit the key, and it fired up instantly and idled perfect. The factory gauges worked perfectly with the Hemi too.

I did end up with 2 engine codes right out of the gate. One was for the downstream 02' sensor on the driver's side, which was an easy fix. The second one was the ECU not recognizing the ignition key, and proved a little more troublesome. Technically, the vehicle shouldn't run if it doesn't recognize the "security key", but (I assume) Hotwire programs that feature out of the ECU. The problem with that comes at emissions testing time. In MD, you can not have a CEL on in order to pass. Luckily, there is a shop local to me that was able to program my key to the ECU. Hotwire programs your vin number into the ECU, but you need an additional 4 digit code from Mopar to make the computer pay attention to the key and turn the light off. One option is to go to the dealership and have them do it for you under the guise of having installed a new computer.

Now, I'm not sure if this story is true, but the guy that fixed mine at the independent shop told me that if a dealership technician thinks your swap is suspect (whether it be emissions related or otherwise), the dealership has the power to basically delete your vin number from the dmv all together. Like I said, I'm not sure if thats true, but I was happy to pay him the $95 for fixing my issue and I was on my way.

All buttoned up and back together:
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How's it drive? I gotta say, the Hemi is A LOT of fun to have under the hood. The 1st thing people usually ask is "How fast is it"? The thing is, the Hemi doesn't really have that "hot rod" kind of feel to the power. The motor just seems to have power everywhere in the power band. It doesn't really like to spin up to high rpm's, it just likes to lug around effortlessly. With 4:56 gears and 35's, I turn 2k rpm's right at 70 miles per hour. It comes out of the hole hard, and will smoke the tires if you want, but its more fun to just drive around at 1/4 throttle and ease into it. The exhaust is quiet enough that I've caught a few people by surprise when they think they're going to jump a light and get in front of the "big slow Jeep". :laughing:

My gas mileage stayed exactly the same between the 4.0 and the Hemi at 14 mpg around town.

Sleeper:

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About 3000 miles into the swap, I suffered the first casualty. The \"new\" replacement Taurus fan that I bought from Rock Auto died. The motor just quit and wouldn\'t run on high or low. I reworked my fan mount, threw a cheap leftover Flexalite fan on it I got for free from my buddy at Appalachian Offroad, and life was good for a while. \n\nA couple thousand miles later, I developed a coolant leak in the radiator. The radiator started to split where the tanks met the core on the driver\'s side. I went back on my ebay account and found I still had 1 more month on my warranty through Superior. Sweet, right?! That is until I got in contact with them. I explained to the guy what was happening and where it was leaking, and that I had basically built my entire cooling system around this radiator. Their answer was for me to take the radiator out, box it up, and send it back to them for \"inspection\". IF they found themselves at fault, they would replace the radiator. When I offered to buy a second radiator and have them refund me once they inspected it, I was basically told to kick rocks. The guy on the phone said that \"they\'ve sold hundreds of these radiators this year, not one has failed\" and \"I know how Jeep guys are, you zip tie a fan to the radiator fins, go out 4 wheeling, and tear the radiator all up\".\n\nFantastic customer service :rolleyes:\n\nSo, at this point I needed to get the Jeep back together asap. I figured, if I\'m gonna get fawked on a radiator in the future, its going to be a cheap one so I bought this one from Amazon: https://www.amazon.com/Aluminum-Radi...1191072&sr=8-1\n\nSince this radiator didn\'t have the bung in it for my temperature sender for my fan, I bought this little guy and put it in the upper radiator hose where I had it coupled together: https://www.amazon.com/Steiger-Perfo...1191148&sr=8-1\n\nI also upgraded my freebie fan to a new Flex a lite bolt-in 13\" fan meant for the Jeep application. \n\nAt this point, the cooling system has been treating me well and runs right where it should temp wise.
 
How much customization was needed for the HVAC, and did you keep AC?
 
How much customization was needed for the HVAC, and did you keep AC?

The heater core lines from the Grand Cherokee worked nearly perfect. The one that goes to the rear of the intake had to be cut and sleeved, but the bends were perfect once it was shortened up.

I do not have AC yet. I kept all of the lines and components from both Jeeps in hopes of just having to get lines made. We'll see how that goes!
 
So, what good is a mall cruising Hemi powered LJ without a rockin' stereo system? :laughing:

I wanted to keep everything hidden and still retain the cargo space of the longer wheelbase. A few years ago there was a guy that was kind enough to put up a cut sheet of his custom designed under seat subwoofer enclosure. Unfortunately, he passed away a couple years back, and his website is no longer available.

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All buttoned up with the seat foam trimmed up and the cover reinstalled

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I took the plans one step further, and used the empty space in the back of the seat to hide the amplifiers.

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I had never wired a stereo back to front before, so that was kind of interesting. All of the cabling has enough slack so that the rear seat can still fold and tumble forward like a stock one.

For high range speakers, I used Polk Audio Db series 2 ways in the stock sound bars. In the front, I bought a set of pods that house a 5 1/4" woofer in the stock dash location and I hid the tweeters in the vents just above them.
 
Great job on the engine swap and back seat. I like how your swap took the "parts bin" approach by using many Jeep/Mopar parts compared to dozens of niche vendor products.
 
Thanks man!

I did find a bunch of threads where guys were using "kits" to swap Hemi's in, primarily using the Ram truck engines. The Grand Cherokee Hemi is technically considered a car engine and is supposed to be more difficult to install. I figured since you need the Grand Cherokee manifolds and throttle pedal l was a couple steps ahead.

Hopefully someone can use this info to find a cheap GC Hemi and throw it in their TJ.
 
Thank you for the detailed tech. I had the chance to by my wife's '17 GC Summit back from insurance after her wreck, but they were asking nearly 80% of the totaled value for it! I guess they sell them overseas to be rebuilt and driven, so they can demand a premium for were totals like hers.

Ill be filing this one in the memory banks hoping for the chance at a similar build.
 
Thank you for the detailed tech. I had the chance to by my wife's '17 GC Summit back from insurance after her wreck, but they were asking nearly 80% of the totaled value for it! I guess they sell them overseas to be rebuilt and driven, so they can demand a premium for were totals like hers.

Ill be filing this one in the memory banks hoping for the chance at a similar build.

Damn, thats crazy. I always compared "totaled" value with "salvage" value, but I guess the grey market for repaired vehicles overseas must be hot!

I'll be honest, I thought the damage to my Sister's Jeep was minimal and easily fixed, but I guess being a 2006 with 100k miles totaled it pretty quick. Her buy back was $2k, and for that I got to pick away at the thing at my leisure. The little nickle and dime stuff would have added up quick if I didn't have it sitting in the driveway to scavenge from.

I didn't mention it earlier, but she also had an Old Man Emu lift on it with aftermarket rims and tires when it was totaled. She wanted that stuff back for the new Grand she bought, so it all worked out in the end.
 
Next up was fuel. Luckily, the 05-06 fuel pumps have enough pressure and volume to keep the Hemi happy. I figured since the pump in the Jeep could potentially have 270K miles on it, a replacement was in order. I swear, every time I need to do a fuel pump, the tank is full.

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I guess an update is in order. When I originally replaced the fuel pump, I simply replaced the pump itself and not the whole sending unit/cartridge/etc. From the very beginning the Jeep had a high rpm stumble prior to shifting into the next gear if you planted your foot to the floor and stood on it. I had attributed this to the tune or something in the ecu because it always seemed to have plenty of power and got down the road pretty good. Since I had never driven a Hemi swapped anything, I was really happy with the power it made.

Well, a few weeks ago I was coming home from work and anything over 1/2 throttle turned the motor into a stumbling blubbering mess and it seemed to be cutting fuel hard. The check engine light would flash and then it stayed on for good. It threw a P0171 and a P0174 code meaning banks 1 and 2 were both lean, and I later learned the flashing CEL means the converters were getting too hot.

Since the fuel rail on the Hemi doesn't have a schrader valve, I had to buy a new fuel pressure test kit: https://www.amazon.com/BETOOLL-Fuel-...9178458&sr=8-1

Once installed, fuel pressure at idle was 58lbs., which is supposed to be sufficient. As soon as I would give it throttle it would drop, and while driving I saw as low as 35psi.:eek:

Soooo, this time I ordered the entire fuel pump assembly, dropped the tank (3/4 full, as usual :rolleyes:), and had it all back together in less than an hour (I had to pat myself on the back for using copious amounts of anti seize on the tank skid hardware) :laughing:

The pump I ordered was a Denso pump, part number 953-3062 and I got it from Rock Auto. That being said, I'm fairly certain any PROPER replacement pump would do the trick, and I would highly recommend not cutting corners like I did the 1st time around.

All that being said, DAMN THIS THING MOVES NOW!!!!!!!!!!!! I can honestly say, dropping the new fuel pump in feels like I added 50 horsepower. You can stand on the go-pedal and the Jeep will pull hard all the way to redline, bang the next gear, and keep pulling. It will also do a standing burnout without the need for any brakes, just pin it and let the tires smoke. :smokin:

Thinking back, the only thing I can come up with is that the local parts store either sold me a junk pump to start, or they sold me a pump for an older 4.0 (pre 05') thinking it would be fine.
 
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How's it drive? I gotta say, the Hemi is A LOT of fun to have under the hood. The 1st thing people usually ask is "How fast is it"? The thing is, the Hemi doesn't really have that "hot rod" kind of feel to the power. The motor just seems to have power everywhere in the power band. It doesn't really like to spin up to high rpm's, it just likes to lug around effortlessly.

Looking back, I can honestly say this is all pretty much bullshit. :lmao:

The LJ is now what I would consider a pretty "fast" Jeep. It will happily rev to redlline and pulls hard all the way up. I can't believe I put over 6k miles on this thing not knowing what I was missing.

I got the thing buttoned up 2 days before my son and I made our annual Father/Son trip to the beach here in MD. They do a big Jeep show every year, and we've been going for the last 5 years, basically as an excuse for the two of us to get away from the women for a week :laughing:. One of the cool things you get out of this event is a once a year permission slip to drive down the beach.

The 3 hour trip to the shore was essentially my "test drive", and the Jeep ran flawlessly. The boy and I had a blast and made it home with the Jeep in one piece.

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I took the plans one step further, and used the empty space in the back of the seat to hide the amplifiers.







I had never wired a stereo back to front before, so that was kind of interesting. All of the cabling has enough slack so that the rear seat can still fold and tumble forward like a stock one.

For high range speakers, I used Polk Audio Db series 2 ways in the stock sound bars. In the front, I bought a set of pods that house a 5 1/4" woofer in the stock dash location and I hid the tweeters in the vents just above them.

Nice, any cooling issues?
 
Would the stock head pipe and catalytic converters have fit if you left the front shaft off?

Why wouldn't the Grand Cherokee PCM work?

Need to know, those items would need to be present and stock for a Commiefornia swap to be smog legal. I have a couple buddies wanting me to do this if I can do it legally. I can leave the front shaft off until it passes the referee inspection. They want the head pipe 100% unmodified.
 
Would the stock head pipe and catalytic converters have fit if you left the front shaft off?

Why wouldn't the Grand Cherokee PCM work?

Need to know, those items would need to be present and stock for a Commiefornia swap to be smog legal. I have a couple buddies wanting me to do this if I can do it legally. I can leave the front shaft off until it passes the referee inspection. They want the head pipe 100% unmodified.

The stock Grand Cherokee head pipe with the converters would fit almost perfectly, the only difference is the 2 bolt flange to the cat back. I cut both flanges off, and welded the LJ flange to the Grand Cherokee down pipe. In my case, I could bolt on any stock or aftermarket cat back.

I couldn't tell you why the stock Grand PCM would not work. I got my harness through Hotwire Auto, and the 05 Ram PCM is the one they specify to work with their harness. From the research I did, there are a few companies that have successfully smogged these swaps with the 05 PCM in California, but I don't know what you would need to keep the referee happy.

I'm in Maryland, and vehicle code says the engine that you swap into the registered vehicle has to be the same year or newer, and pass the state's emission's test. That being said, our emissions testing is simply an OBD II test performed by a state employee at a state inspection facility. If you're CEL isn't on and their scanner agrees with that fact (as in, you haven't cleared any hard codes prior to testing), you're good to go. They do a visual inspection, but it usually consists of the employee waving a mirror under your car while they wait for the scanner to do its thing.
 
Thanks, as long as the flange was behind the last cat and O2 sensor/s you can modify it in commiefornia.
 
I love this subwoofer and amplifier mounting idea!!! With the sub box under there, does that affect the comfort of the rear seat? If it is not affected, I will be doing this for sure!
 
I love this subwoofer and amplifier mounting idea!!! With the sub box under there, does that affect the comfort of the rear seat? If it is not affected, I will be doing this for sure!

You end up with about 1.5-2 inches of foam on the bottom of the seat once you trim it up, and the back is unaffected. I have had a couple adults ride back there for short trips, but it was mostly to show off the motor or the stereo, so all opinions have been pretty positive :laughing:

My butt-o-meter tells me it would be as bareable as any other cramped trip in the back seat of a Jeep. My kids absolutely love it, so there is that too.

I wish l had saved the plans from the site l got them from, but since the designer passed away, lm not sure if they are out there anymore or not. His plans gave you great instructions and a cut sheet for every piece you needed to build the enclosure.
 
Thanks for the info. I guess it all really depends on the sub used. Could find a woofer that needs as little volume as possible and end up with more cushion if I really want to.
 
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