Engine upgrades?

Sasquatch · Jun 17, 2015

I know the stock engine can't handle boost. But are the parts available to fix this? My KJ has a "new" engine already. But at some point it will need rebuilding or replacing. It just seems like it would be a lot simpler to upgrade the engine and add turbos or a blower for more power than to swap an eight in. Although swapping an eight would also give me the opportunity to swap in a manual instead of the slushbox.

tommudd · Jun 17, 2015

Would need different pistons and everything
lots has been tried in the past and didn't work
Has enough power to get you everywhere, regearing helps more than anything

twowings · Jun 17, 2015

Exactly how much power do you need?

Properly maintained, the 3.7L has plenty of power for the KJ...I'm running 245/75R/16s on 3.73 gears and loaded to the grab bars with luggage, tools, and vacation crap, and I'm STILL able to run 75-80 mph and keep up with interstate traffic...I'd seriously suggest looking elsewhere for something to hot-rod...if you ever intend to offroad, all that performance stuff is useless anyway crawling along at 1 mph...YMMV

As for a V8 swap, good luck with THAT, pilgrim!

Sasquatch · Jun 17, 2015

twowings said:
Exactly how much power do you need?

More.

tommudd · Jun 17, 2015

New Mustangs are nice if you need more power:icon_lol:
The KJ is what it is, a great vehicle with enough power to move itself pretty good

CzarKJ · Jun 17, 2015

Could try a fastman throttle body for a little more feel of oomph. Might squeeze a few hp out.

Sasquatch · Jun 17, 2015

tommudd said:
New Mustangs are nice if you need more power:icon_lol:
The KJ is what it is, a great vehicle with enough power to move itself pretty good

By that logic, it's wrong to modify a KJ in any way. They are what they are. No need for taller tires, they move pretty good across trails as they are. No need for a winch, you can call a tow truck. No need for a better stereo or speakers, the stock ones make pretty good sound as is. Don't do anything to your vehicle. The engineers got it perfect at the factory.

I don't own a Mustang, I own a KJ. If I had $35,000 laying around to buy a Mustang I might do so. But I don't have $35,000 laying around. I also need more cargo space than a Mustang offers. Which makes the Liberty a slightly better option for me. I can't afford eight different cars to serve eight different purposes. So I have to make one car suit as many needs as possible. And that includes making me smile when I'm behind the wheel. And that means more power. I can add more power for a lot less money than I'd spend to buy a more powerful car.

Plus, it's my Jeep. If I feel it needs more power then it is my option as a free-ish American to add more power to it. Just because you feel the power is adequate does not mean everyone else must be happy with it. So don't tell me I need to buy something else if I want more power.

If you know of others who have failed at upgrading their engines, great. Show me the links so I can see what went wrong. I find it hard to believe there's an engine that can't be rebuilt stronger than it was. Pics or it didn't happen.

Sasquatch · Jun 17, 2015

CzarKJ said:
Could try a fastman throttle body for a little more feel of oomph. Might squeeze a few hp out.

I'll add that to the list of options. Thanks.

John3seventeen · Jun 17, 2015

Sasquatch said:
I'll add that to the list of options. Thanks.

Hipotek makes a nice throttle body, and I believe the suggestion of gears was made it will put more power to the ground. People aren't trying to limit what you do sadly the KJ does. Most things have been tried and the failures and successes recorded here and on LOST. Read on and best of luck !

Hedsic · Jun 17, 2015

Sasquatch said:
By that logic, it's wrong to modify a KJ in any way. They are what they are. No need for taller tires, they move pretty good across trails as they are. No need for a winch, you can call a tow truck. No need for a better stereo or speakers, the stock ones make pretty good sound as is. Don't do anything to your vehicle. The engineers got it perfect at the factory.

I don't own a Mustang, I own a KJ. If I had $35,000 laying around to buy a Mustang I might do so. But I don't have $35,000 laying around. I also need more cargo space than a Mustang offers. Which makes the Liberty a slightly better option for me. I can't afford eight different cars to serve eight different purposes. So I have to make one car suit as many needs as possible. And that includes making me smile when I'm behind the wheel. And that means more power. I can add more power for a lot less money than I'd spend to buy a more powerful car.

Plus, it's my Jeep. If I feel it needs more power then it is my option as a free-ish American to add more power to it. Just because you feel the power is adequate does not mean everyone else must be happy with it. So don't tell me I need to buy something else if I want more power.

If you know of others who have failed at upgrading their engines, great. Show me the links so I can see what went wrong. I find it hard to believe there's an engine that can't be rebuilt stronger than it was. Pics or it didn't happen.

I think it was more of a hypothetical suggestion and his way of basically saying that there really is nothing out there.

A regear is going to give you the most improvement and about the most you can do. It doesn't give you more power but will channel it better.

Trust me, if there was something out there, I'm pretty sure half of this board would be all over it like white on rice.

It's not really Tom's fault that no-one has really found anything to give much gain out of the KJ motor. He's just the messenger so getting upset with him for answering your question is counter productive. Trust me, from experience, when newer users get upset or attitudes towards moderators for trying to help(even if it's not the answer you wanted), It usually makes the rest of the board not want to participate and help anymore.

Honestly, Your best bet is to use your mechanical skills and see what you can come up with because there isn't much out there to buy. Maybe you can find something everyone else has missed or overlooked. Whatever it is, I bet you will make a pretty penny off of it if it truly does offer some decent power gains for the cost.

04Liberty · Jun 17, 2015

It's true, there isn't much. V8 swap has happened, but we don't have any updates long term; it's a helluva lot of work, fab, etc. Hypertech makes a programmer, but it starts with the 04's and goes up. One alternative that I used before Hypertech came out with their programmer is hemifevertuning.com. He figured that certain early (02-04) Liberty PCM's were compatible with the SCT 9550 tuner. If the PCM part number is compatible then he can custom tune it, either generic programmer style 'canned tunes' or custom tuned to a combo. Almost anything that can be done to a 4.7 can be done to a 3.7, so there are parts that can be used, unfortunately cams (unless custom ground) are out of the question. There used to be a supercharger kit years back that was discontinued; ring lands are too high on the stock pistons and don't hold up well under boost. Most people don't want to go through the expense of replacing pistons. As stated, a gear change will get you the biggest bang for buck for getting power to pavement. Do you know if you have a 42RLE or the 45RFE? If you have the RFE then there's all kinds of stuff available for that. Just some ideas.

JasonJ · Jun 17, 2015

Having come from a time of adding turbchargers to everything I own (I had two IHI turbo equipped Ford Escorts that I built, so yeah...) I can add something to this.

I am sure the 3.7 can be rebuilt to handle whatever you want... but it's going to cost you a ton of cash. Maybe you have a ton of cash you can throw at it. Fine.. good on you. But here's the thing, it's going to be a $10k bill to properly rebuild/reengineer the 3.7 to handle decent amounts of boost pressure, including the cost of the turbo components themselves.

What I would do if I were in your place, and this is just me, feel free-ish to do what you like, is consider, CONSIDER replacing the KJ with an equivalent model year Grand Cherokee. It'll give you more cargo room than the Liberty will. You can get it with the 4.7 HO v8 already in place. So there is a good bump in power there. The 4.7HO puts out 265hp and a very nice 325ft lbs of torque.

Depending on the mileage on your KJ, you could almost and most likely break even on the pricing and purchase costs of the upgrade as well.

Good luck with your search for what makes you happy.. I hope you find it.

tommudd · Jun 17, 2015

Sasquatch said:
By that logic, it's wrong to modify a KJ in any way. They are what they are. No need for taller tires, they move pretty good across trails as they are. No need for a winch, you can call a tow truck. No need for a better stereo or speakers, the stock ones make pretty good sound as is. Don't do anything to your vehicle. The engineers got it perfect at the factory.

I don't own a Mustang, I own a KJ. If I had $35,000 laying around to buy a Mustang I might do so. But I don't have $35,000 laying around. I also need more cargo space than a Mustang offers. Which makes the Liberty a slightly better option for me. I can't afford eight different cars to serve eight different purposes. So I have to make one car suit as many needs as possible. And that includes making me smile when I'm behind the wheel. And that means more power. I can add more power for a lot less money than I'd spend to buy a more powerful car.

Plus, it's my Jeep. If I feel it needs more power then it is my option as a free-ish American to add more power to it. Just because you feel the power is adequate does not mean everyone else must be happy with it. So don't tell me I need to buy something else if I want more power.

If you know of others who have failed at upgrading their engines, great. Show me the links so I can see what went wrong. I find it hard to believe there's an engine that can't be rebuilt stronger than it was. Pics or it didn't happen.

Here we go again, must be about 90 day limit, I'm not taking my time to look up each article but if you look up KYLIBERTY he tried several things as far as boost etc way back in the early years. None worked and he still may have the blown engines to prove it.
Bud I was just making an off the wall joke in the Mustang but sad fact is THERE IS NOT MUCH you can do, period. Heck even the company making headers quit due to a couple of things but even they didn't do that much.
As far as lifting / adding lockers etc that is a whole different thing than what we are discussing here, we have found what works and works great
Like I stated these engines are what they are, period
Would more power be nice? at times maybe. I grew up and built plenty of hot rod type cars back in the 70/80s . I have owned 427 Corvettes, AAR Cudas, 390 Mustangs, 55 Chevy with a 302 Z-28 motor etc. I know what fun it is to have some extra horsepower. But to wring a small amount of these engines its going to be half of what one of these cost brand new
Now blow off at me again for not knowing or helping :icon_lol:

Sasquatch · Jun 17, 2015

Hedsic said:
I think it was more of a hypothetical suggestion and his way of basically saying that there really is nothing out there.

A regear is going to give you the most improvement and about the most you can do. It doesn't give you more power but will channel it better.

Trust me, if there was something out there, I'm pretty sure half of this board would be all over it like white on rice.

It's not really Tom's fault that no-one has really found anything to give much gain out of the KJ motor. He's just the messenger so getting upset with him for answering your question is counter productive. Trust me, from experience, when newer users get upset or attitudes towards moderators for trying to help(even if it's not the answer you wanted), It usually makes the rest of the board not want to participate and help anymore.

Honestly, Your best bet is to use your mechanical skills and see what you can come up with because there isn't much out there to buy. Maybe you can find something everyone else has missed or overlooked. Whatever it is, I bet you will make a pretty penny off of it if it truly does offer some decent power gains for the cost.

If I had asked, "how do I lift my KJ?" and he had replied, "you don't need to lift it, it's plenty high enough for what it is" would we even be having this discussion? I'm not trying to turn my KJ into a Lamborghini. There are just times when it is too slow for my taste. That underlined part is important. There are tons of rigs on here with mods I personally think are useless. But I'm not telling people that because I figure they know what they want/need and it's not my place to tell them they're wrong about their desires. If he's happy with the power of his KJ, great. That doesn't grant him god-like authority to tell me I should be happy with it too. Now, pointing out, as you did, the complications of adding power to this particular engine is a different matter. If there are design flaws in the engine that make adding power impossible or ridiculously expensive, then that's a factor I have to consider. If there are no parts available due to lack of demand, then that's a factor to consider. But someone else's desires or preferences absolutely never under any circumstances have any relevance to what I am doing. His answer was not phrased, "you can't do it because..." is answer was phrased, "you shouldn't do it because I don't think it's necessary". Yes, that "I will decide what you need" attitude always makes me angry. I don't know why it's so universal on car forums. A productive, civil response pointing out hurdles or potential dangers is great. But a response which merely belittles or dismisses the OP's goals is entirely un-called for. Even ridiculous questions deserve serious answers because serious answers actually educate people. Nobody will learn anything from, "yer an idjit, buy a Civic".

My mechanical skills are part of the problem. I have a pathological need to tinker. I don't feel like I own a car until I have done something to improve it. I have tinkered with each and every one of the thirty or so cars I have owned. Not surprisingly, some of this tinkering has been more successful than others. :emotions34: But screwing up only teaches you how to fix things better.

I honestly think folks sometimes miss out on parts that are available because they don't look for them after being told not to bother. For example, the reason we can't put turbos or blowers on the 3.7 is because the pistons are too weak to handle the added power. But nobody ever mentions that for $200 at Summit Racing you can get a set of Kieth Black hypereutectic pistons that are designed with reinforced ring lands. Those should easily handle modest boost levels. I don't know what stock pistons cost. But $200 doesn't seem ridiculous for aftermarket pistons. If you're rebuilding an engine anyhow, why not throw in those pistons instead of stock replacements?

Also, JBA offers shorty headers they claim are designed for the Liberty. At like $520 they aren't cheap. But if they fit they could be worth some power.

It seems a couple different companies offer tuners. I'm always skeptical of those. Especially if you have other modifications. I just don't think a generic "power" tune will offer significant improvement over stock or respond any better to mechanical mods. So I don't know if the stock ECM could be retained with mechanical mods because I don't know if it can be custom programmed to suit what's been done.

There are at least two different successful V-8 swaps on Youtube. So I know that's an option. But it looks much more complicated than adding power to the 3.7. Still, if I could find a V-8/manual Dakota donor I would be tempted.

Regearing is definitely an option. There are tradeoffs to consider there like everything else. I don't even know what gears I have at the moment. I do want a limited slip. Regearing wouldn't add much to the cost of installing a new diff.

Honestly, the best return-on-investment may have nothing to do with power. I might get sufficient driving enjoyment simply by swapping in a manual. I hate automatics. And that's a swap I might make for free if I could find somebody with a manual who wanted to switch to an auto. Trade keys, do some paperwork, swap done. Any takers?

Sasquatch · Jun 17, 2015

04Liberty said:
It's true, there isn't much. V8 swap has happened, but we don't have any updates long term; it's a helluva lot of work, fab, etc. Hypertech makes a programmer, but it starts with the 04's and goes up. One alternative that I used before Hypertech came out with their programmer is hemifevertuning.com. He figured that certain early (02-04) Liberty PCM's were compatible with the SCT 9550 tuner. If the PCM part number is compatible then he can custom tune it, either generic programmer style 'canned tunes' or custom tuned to a combo. Almost anything that can be done to a 4.7 can be done to a 3.7, so there are parts that can be used, unfortunately cams (unless custom ground) are out of the question. There used to be a supercharger kit years back that was discontinued; ring lands are too high on the stock pistons and don't hold up well under boost. Most people don't want to go through the expense of replacing pistons. As stated, a gear change will get you the biggest bang for buck for getting power to pavement. Do you know if you have a 42RLE or the 45RFE? If you have the RFE then there's all kinds of stuff available for that. Just some ideas.

It's only recently that I've decided to (probably) keep the KJ. So I haven't done much research yet on what I have. No idea what PCM or transmission I have. I have found out that there are aftermarket hypereutectic pistons that should easily handle sane levels of boost. So a blower is a likely option for the future. But I can guarantee nothing will be happening this month.

JasonJ said:
Having come from a time of adding turbchargers to everything I own (I had two IHI turbo equipped Ford Escorts that I built, so yeah...) I can add something to this.

I am sure the 3.7 can be rebuilt to handle whatever you want... but it's going to cost you a ton of cash. Maybe you have a ton of cash you can throw at it. Fine.. good on you. But here's the thing, it's going to be a $10k bill to properly rebuild/reengineer the 3.7 to handle decent amounts of boost pressure, including the cost of the turbo components themselves.

What I would do if I were in your place, and this is just me, feel free-ish to do what you like, is consider, CONSIDER replacing the KJ with an equivalent model year Grand Cherokee. It'll give you more cargo room than the Liberty will. You can get it with the 4.7 HO v8 already in place. So there is a good bump in power there. The 4.7HO puts out 265hp and a very nice 325ft lbs of torque.

Depending on the mileage on your KJ, you could almost and most likely break even on the pricing and purchase costs of the upgrade as well.

Good luck with your search for what makes you happy.. I hope you find it.

I am considering all sorts of trade options. Even knowing there are upgraded pistons that will handle boost doesn't mean boosting this teeny engine is the best way to go. And I definitely like the GC far better than I like the KJ. But, honestly, if I do trade it will probably be for something much older and bigger. I can step back in time to the days before electronics infested automobiles and get a wagon big enough to park a KJ in the back. Sure, the MPG would suck. But the KJ isn't exactly a Prius anyhow.

CactusJacked · Jun 17, 2015

I say do the 4.7 swap and prove all the nay-sayers wrong. It has been done successfully before, so you can too as long as this kind of task is within your skill set. Sure you can enhance the 3.7, but it still won't have the torque of a V8. I know where you're coming from, people thought I was nuts and it couldn't be done when I put a Chevy 350 in my Datsun pickup, or a 4.3 in my Samurai. The Datsun was for the fun of it. The Zuki was too, but also because those whopping 1.3L 4 bangers are less than anemic, and 31" tires didn't help it either. There was nothing more satisfying than blowing by another Samurai as theirs was huffing and puffing just to try to beat a head wind!

dude1116 · Jun 17, 2015

I want to see a v8 swap come back to the forum after being swapped for a week :shrug:

KYLiberty · Jun 17, 2015

tommudd said:
Here we go again, must be about 90 day limit, I'm not taking my time to look up each article but if you look up KYLIBERTY he tried several things as far as boost etc way back in the early years. None worked and he still may have the blown engines to prove it.
Bud I was just making an off the wall joke in the Mustang but sad fact is THERE IS NOT MUCH you can do, period. Heck even the company making headers quit due to a couple of things but even they didn't do that much.
As far as lifting / adding lockers etc that is a whole different thing than what we are discussing here, we have found what works and works great
Like I stated these engines are what they are, period
Would more power be nice? at times maybe. I grew up and built plenty of hot rod type cars back in the 70/80s . I have owned 427 Corvettes, AAR Cudas, 390 Mustangs, 55 Chevy with a 302 Z-28 motor etc. I know what fun it is to have some extra horsepower. But to wring a small amount of these engines its going to be half of what one of these cost brand new
Now blow off at me again for not knowing or helping :icon_lol:

I was able to get over 300 HP and 350 LBFT torque to the ground with the 3.7. Took about 1 year to scorch a couple cylinders and ended up dropping a new short block in it. The heads were polished, ported, and rebuilt. I still have the bad short block in my garage because I was going to build a supercharged motor out of it but came to my senses.

If you have an early KJ with the 45RFE, you can definitely upgrade the transmission. You can get a little better air flow, but colder air is needed too and there are only a handful of the cold air hoods out there. A custom aggressive tune from B&G Chrysler is helpful. Your best bet is to regear to 4.10s though.

Of course, once I finish the short bed Scrambler conversion on my JKR in a couple months, I'll probably be selling the KJ. It's never had N2O on this motor, transmission, or rear differential. About 80K on this motor and about 6K on this transmission. It's not stupid fast like it was, but performs much better than stock. It will be a way for someone to get a well built KJ.

tommudd · Jun 17, 2015

Sasquatch said:
If I had asked, "how do I lift my KJ?" and he had replied, "you don't need to lift it, it's plenty high enough for what it is" would we even be having this discussion? I'm not trying to turn my KJ into a Lamborghini. There are just times when it is too slow for my taste. That underlined part is important. There are tons of rigs on here with mods I personally think are useless. But I'm not telling people that because I figure they know what they want/need and it's not my place to tell them they're wrong about their desires. If he's happy with the power of his KJ, great. That doesn't grant him god-like authority to tell me I should be happy with it too. Now, pointing out, as you did, the complications of adding power to this particular engine is a different matter. If there are design flaws in the engine that make adding power impossible or ridiculously expensive, then that's a factor I have to consider. If there are no parts available due to lack of demand, then that's a factor to consider. But someone else's desires or preferences absolutely never under any circumstances have any relevance to what I am doing. His answer was not phrased, "you can't do it because..." is answer was phrased, "you shouldn't do it because I don't think it's necessary". Yes, that "I will decide what you need" attitude always makes me angry. I don't know why it's so universal on car forums. A productive, civil response pointing out hurdles or potential dangers is great. But a response which merely belittles or dismisses the OP's goals is entirely un-called for. Even ridiculous questions deserve serious answers because serious answers actually educate people. Nobody will learn anything from, "yer an idjit, buy a Civic".

My mechanical skills are part of the problem. I have a pathological need to tinker. I don't feel like I own a car until I have done something to improve it. I have tinkered with each and every one of the thirty or so cars I have owned. Not surprisingly, some of this tinkering has been more successful than others. :emotions34: But screwing up only teaches you how to fix things better.

I honestly think folks sometimes miss out on parts that are available because they don't look for them after being told not to bother. For example, the reason we can't put turbos or blowers on the 3.7 is because the pistons are too weak to handle the added power. But nobody ever mentions that for $200 at Summit Racing you can get a set of Kieth Black hypereutectic pistons that are designed with reinforced ring lands. Those should easily handle modest boost levels. I don't know what stock pistons cost. But $200 doesn't seem ridiculous for aftermarket pistons. If you're rebuilding an engine anyhow, why not throw in those pistons instead of stock replacements?

Also, JBA offers shorty headers they claim are designed for the Liberty. At like $520 they aren't cheap. But if they fit they could be worth some power.

It seems a couple different companies offer tuners. I'm always skeptical of those. Especially if you have other modifications. I just don't think a generic "power" tune will offer significant improvement over stock or respond any better to mechanical mods. So I don't know if the stock ECM could be retained with mechanical mods because I don't know if it can be custom programmed to suit what's been done.

There are at least two different successful V-8 swaps on Youtube. So I know that's an option. But it looks much more complicated than adding power to the 3.7. Still, if I could find a V-8/manual Dakota donor I would be tempted.

Regearing is definitely an option. There are tradeoffs to consider there like everything else. I don't even know what gears I have at the moment. I do want a limited slip. Regearing wouldn't add much to the cost of installing a new diff.

Honestly, the best return-on-investment may have nothing to do with power. I might get sufficient driving enjoyment simply by swapping in a manual. I hate automatics. And that's a swap I might make for free if I could find somebody with a manual who wanted to switch to an auto. Trade keys, do some paperwork, swap done. Any takers?

Man I am just so stupid aren't I, :happy175::happy175::happy175:never look at Summit or Jegs for parts, or even knew JBA has headers advertised OH WAIT we do look at those things BUT, oh well I have much better things to do that rationalize why or why not some do some don't

tommudd · Jun 17, 2015

Sasquatch said:
There are at least two different successful V-8 swaps on Youtube. So I know that's an option. But it looks much more complicated than adding power to the 3.7. Still, if I could find a V-8/manual Dakota donor I would be tempted.

Saw those funny thing is one was done and traded off really quick ( since it was a big old pile of doo doo, other one there was a vid made and then it disappeared. One guy on here did one, made a vid of it backing out of the garage with a few things needing finished and then he disappeared. haven't really seen one long term ( over a few days) yet

Engine upgrades?

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