Why does the crowd seem to favor an LS swap over a Hemi?

Now that the crowd here has helped me settle on the suspension build and has talked me out of a supercharger, I'm fast forwarding the planning to the next step. My wallet will need to recover for a few months, but I'm HOPING to be ready to swap my 3.6 for a v8 in the sept/oct timeframe.

It seems that most here favor the LS platform over the Hemi and I'm wondering why. It seems that the integration with factory systems such as guages, dashboard, transmission, etc would be so much more complex with an LS. You'd lose use of the factory EVIC display with an LS. Not a deal breaker but it's definitely not as elegant. What other reasons? Cost? Seems that the cost is roughly a $5k difference. The Hemi even has well thought out engine swap kits from AEV. The primary downfall of the hemi in my book is the fuel consumption. The 6.4 in my GC SRT-8 was damned thirsty and I can't imagine how bad it would be with 37" beadlocks and brick wall aerodynamics. I've heard it's the head design of the Hemi's that makes them less efficient. What else has the crowd here considered when favoring an LS?

Weight, price, and a strong tendency to overheat are some of the reasons I have heard people complain about Hemis.

I've heard weight is one of the factors as the L's weighs nearly the same as the 3.8

Subscribed...curious about this as well.

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Lighter..tons of aftermarket performance parts... Better Mpgs. Better transmission. Can easily get 300 thousand miles out of them (I have over 300 thousand on my suburban )

One thing that may sway your decision is the year of your jk. You stated you want to swap the 3.6. I could be wrong but I believe Motech's LS swaps only cover the 07-11 JKs. I haven't heard of anyone swapping a 3.6 for an LS, only a 3.8. The good thing about the 3.6 j is if you do a hemi swap you can use the a580 trans (what you have in jk now). Many people beef it up a bit. You essentially will have the same power train that was in your GC SRT if you swap in the 6.4 assuming you have a 12/13 SRT that had the 5 speed vs the 14 with the 8 speed.

Sharkey said:

Weight, price, and a strong tendency to overheat are some of the reasons I have heard people complain about Hemis.

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^This^

I have talked with Florida Highway Patrol officers on several occasions on motor vehicle accidents and nearly every one of them say the power is excellent but they have overheating problems......the last one I spoke with told me his particular vehicle is on it's third motor.........granted they beat on them pretty hard and the heat down here in South Florida during the 51 weeks of Summer that we have doesn't help things either.......maybe they cooling system design is flawed and that's what is causing the issues and not so much the motor design.......

~Woodrow~

Im courious about an EcoBoost swap... still a v6 with plenty of power and sweet mpg. Wonderbif it would be feasible soon enough...

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HEMI's are great motors and AEV does make the best "kit" for it. It comes with great instructions and is something that a good home mechanic can install without too much fuss. The biggest problem with HEMI's is that they really aren't the best fit for a JK. The biggest problem with them is that you just can't get enough cooling with the size radiator that a JK can accept without modifications and because of it, most of the guys I know with one have over-heating issues. I should note that this is even with the jet engine like fans that always have to be running to keep them cooler and they'er so damn loud that you can't even hear the otherwise awesome sound of the motor. Of course, this is to say nothing about how much gas they drink, how much heavier they are and how you need to beat in your firewall in order to make it fit.

In a nutshell, we went with an LS as so far, we have not had any over heating issues, it's been very easy to program, is lighter weight, is smaller, fits way better in a JK, there's tons of aftermarket support, is tunable, offers better MPG and comes with a great 6L80 transmission. When we got ours, it was far from a complete kit and we did have issues that ultimately required us to take our Jeep to Motech to get squared away but, after they worked on it, it's been great ever since. It is my understanding that the kit is much more complete now and assuming that it is, it's what I would recommend. That, or have Motech install it for you would be the way to go.

Here is a link to our build thread:

http://wayalife.com/showthread.php?6765-It-s-Time-to-SUPERSIZE-Moby-MoTech-6-2L-LS-Jeep-Motor-Swap

Motech is doing swaps of the 3.6 but I think it is in house only yet, not in a kit form. You need to take some extra steps like re-programing the dash and such to make it work correctly. His kits now only consist of three wires in the dash and you use the stock cruise control with no lights on the dash and you will have bump shift in your stock shifter after you are done. It will work just like it did before.
My biggest reason for going with the LS was there are a ton of people to go to if you do have problems and even more for aftermarket parts and tuning etc.. On the Mopar side GOOD LUCK! The CanBus is so convoluted that their are very few that can trouble shoot this system! Just because you throw a code that says you have a bad wheel sensor does not necessarily mean its the wheel sensor. It could be the ABS computer but your Starscan does not tell you that! Technicians biggest complaint I hear is you are forced to shotgun your troubleshooting because of the layout of Chrysler's CanBus. On a GM system you play the process of elimination and loop the CanBus back on itself till the issue goes away then work your way back out from the ECM. You can't do this on a Chrysler system since it kind of works like a star network with the TIPM or fuse box as the signal cop. All modules rely on each other to complete commands for the most part and in theory is less complicated. GM spent ALOT of money on there computers and programs to get things right but it is not perfect either but close! Now add in a foreign model motor to a platform that was not designed to support it and you have added a major amount of complexity to the whole system and as Eddie pointed out the thermal dynamics of this platform are not even close to what the truck platform has. Pop the hood of a truck now imagine this piece of iron in your little jeep engine bay and or even a Chrysler 300 platform it is stuffed in there. I went through this same scenario in my Duramax when they switched from a fixed vane to a variable vane turbo. Never overheated till I bought a bigger camper and a hot day. Now that platform has a second smaller radiator in series with the main and it hasn't had an issue since but people screwed around with this for several years before figuring it out.
If you have doubts go drive one of each and see, feel the differences. The one thing to consider also is to be CARB compliant you need to have the same year or newer motor transplanted into the jeep. Now with a new jeep that means you need to put in a DI LS motor. I haven't talked to Robbie at Motech on this so I have no idea if he has done it yet. If I had to guess he is either working on it or has done them. Talk to these guys that do them! Once you get past all of the acronyms they can put in a sentence they know there stuff. If not they would not be in business yet.

I would say they are both great options, go with the engine you want the most. I went with a Hemi and have had 0 engine related problems, I choose to have a mechanical fan installed with the 6.4 and a small (quiet) electric pusher fan. To date I have had 0 overheating issues, however I have not had the chance to test it in extreme heat. Will be in Moab in this June, so hopefully that will get my heat testing done.

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xflstl said:

I would say they are both great options, go with the engine you want the most. I went with a Hemi and have had 0 engine related problems, I choose to have a mechanical fan installed with the 6.4 and a small (quiet) electric pusher fan. To date I have had 0 overheating issues, however I have not had the chance to test it in extreme heat. Will be in Moab in this June, so hopefully that will get my heat testing done.

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To be fair, most of the guys I know with HEMI's and have no problems either live in flat states or trailer their rigs everywhere. The ones that actually drive their Jeeps to remote locations out here in the west and in the mountains ALL have overheating issues.

wayoflife said:

To be fair, most of the guys I know with HEMI's and have no problems either live in flat states or trailer their rigs everywhere. The ones that actually drive their Jeeps to remote locations out here in the west and in the mountains ALL have overheating issues.

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Do they ALL have mechanical fans? Or do most have the by far more typical electric only fan setup.
I did a ton of research into the Hemi over heating before having my swap done. What I found is that ever case of overheating (that I was able to chit-chat) with the owner had several thing's in common. 1. All but one was an Aev build the odd one was a do it yerselfer that had from what he told me part aev and part burnsville in his setup. 2. More than half of them had modified cut up or removed there inner fenders (which can screws up proper air flow).
3. Every one of them had electric only fans.
Now im not defending Hemi's, as it is commonly known they have overheating issues. Nor am I saying that my setup is perfect, as none are.
I am saying that if you plan accordingly, and build with the overheating issue in mind it can be avoided.
I have not crawled my setup in extreme heat yet. I have however driven in mountains no problems, flat towed a 5500 jku with it, at speeds upto 85mph, as well as drove the snot out of it in temps just over 100. Only thing I overheated was my steering fluid due to a very sub par cooler.


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Seems to hit and miss with the Hemi's, I've read LOTS of overheating issues, and like xflstl said it's the elec fan guys that have the overheating issues.

Now with that being said I've been running my hemi with the factory elec fan and only had issues when the fan motor died on my old lady and it over heated.

Cracked the radiator and all... Big mess! So got a nice big ol radiator custom made at JeepSpeed, slapped in a cooler t-stat, and running a 70-30 coolant mix. I also tried an aftermarket fan which didn't last long and was extremely annoying it was so loud.

So back to the factory fan I went. Runs cool as a cucumber now. ZERO issues pulling the grape vine, cajon, and a few trips up the 14, 395 and the 10 out to Phoenix. Hottest it's gotten was 220 ish pulling the 10 at the chichaccaro (<-- don't remember the name) summit at about 90* outside at about 65mph.

And survived temps of 110+ while in the hot ass AZ desert.

Now if I was gonna do it all over again it would definitely be a 6.2ls 6L80 setup.

Too damn hot for my blood!!

xflstl said:

I would say they are both great options, go with the engine you want the most. I went with a Hemi and have had 0 engine related problems, I choose to have a mechanical fan installed with the 6.4 and a small (quiet) electric pusher fan. To date I have had 0 overheating issues, however I have not had the chance to test it in extreme heat. Will be in Moab in this June, so hopefully that will get my heat testing done.

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I am very concerned about potential overheating. Living in Houston, we have HEAVY humidity which is very detreimental to radiator efficiency. Wondering if most guys use a 3 pass high end radiator like a Ron Davis or something similar? On custom cars, it seems that the cars in humid areas experience cooling problems where they may be less prevalant elsewhere. The LS sounds nice, but after hearing about the Moby build, it looks like there were a fair share of problems that could be an epic PITA. There is no question that I would send it to a reputable builder, but just dont want electrical gremlins to plague me for months. In terms of builders there is Motech and Bruiser? Anyone else? Pros cons of each?

SmokinV10 said:

I am very concerned about potential overheating. Living in Houston, we have HEAVY humidity which is very detreimental to radiator efficiency. Wondering if most guys use a 3 pass high end radiator like a Ron Davis or something similar? On custom cars, it seems that the cars in humid areas experience cooling problems where they may be less prevalant elsewhere. The LS sounds nice, but after hearing about the Moby build, it looks like there were a fair share of problems that could be an epic PITA. There is no question that I would send it to a reputable builder, but just dont want electrical gremlins to plague me for months. In terms of builders there is Motech and Bruiser? Anyone else? Pros cons of each?

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I cant really give you good advise as to where to go, however I can certainly tell you where not to go. I was ripped off by Brunsville offroad, by a guy named Dan Mckeg. While his shop did do excellent work for the most part. He did manage to rip me off by installing lessor parts than were paid for. He is with a Company called Dakota Customs now, so my good advise is stay away from there.

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wayoflife said:

... even with the jet engine like fans that always have to be running to keep them cooler and they'er so damn loud that you can't even hear the otherwise awesome sound of the motor...

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LOL. Yes, this is a problem. A couple years ago, I had the pleasure of being chased by what sounded like a landscaper with a gigantic leaf blower for most of a weekend trip

:cheesy:

wayoflife said:

Here is a link to our build thread:

http://wayalife.com/showthread.php?6765-It-s-Time-to-SUPERSIZE-Moby-MoTech-6-2L-LS-Jeep-Motor-Swap

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Read through the build thread. Looks like you put up with your fair share of frustration trouble shooting the conversion. Did the random issues slow down in frequency? Would you say that your Jeep is now "reliable"?