Higher horses, higher revs & even higher torque, a streetable LJ engine swap

[Rick Flair]

If it was even 270hp. Lol. I need to keep in mind that if it wasn't for the issues I did enjoy that little of power (although I had been planning on building a supercharger stroker for another 100hp...). It's easy to say "I want 1000hp" but as Chris alluded to, too much power can become un-fun.



So far the engines that have caught my eye are the 495hp LS3 and the 627hp LSX 454. The 525hp LS3 I fear could be too lopey to be drivable crawling offroad (although the chop sounds great imo). The LSA seems to be more complex than I'm wanting in my Jeep.

Go LS3, simple and loads of power and can grow if you wish. Should be on the cheaper end too.

You want to keep it driveable and sane. 500 horses is nothing to sneeze at!

 

[toximus]

I think part of why I think I want more is that every modern production LS I've driven (from Silverado, to Escalade, to CTS-V) has been extremely disappointing the way they tune them with a lot of lag on throttle input and slow power ramp for comfort. They make a 400hp+ V8 seem milder than than my ~270hp supercharged 4.0.

 

[Rick Flair]

I think part of why I think I want more is that every modern production LS I've driven (from Silverado, to Escalade, to CTS-V) has been extremely disappointing the way they tune them with a lot of lag on throttle input and slow power ramp for comfort. They make a 400hp+ V8 seem milder than than my ~270hp supercharged 4.0.

Torque management sucks!!!!

 

[Apparition]

I think part of why I think I want more is that every modern production LS I've driven (from Silverado, to Escalade, to CTS-V) has been extremely disappointing the way they tune them with a lot of lag on throttle input and slow power ramp for comfort. They make a 400hp+ V8 seem milder than than my ~270hp supercharged 4.0.

Modern vehicles are deceptive. My ecoboost F150 can embarrass most other trucks when it comes to acceleration but it’s so quiet you don’t realize it. That’s in factory form.

My tuner claims it adds 50HP/TQ on the 87 tune and 90HP/TQ on the 93 tune. That thing becomes an animal performance wise when running those tunes. Still quiet as a mouse.

I’d rather push a Ford than drive a Chevy but I would LS swap if I felt I needed it. LS3 400HP and 400TQ NA is where I’d planned if I did it.

 

[taylormade73]

I think part of why I think I want more is that every modern production LS I've driven (from Silverado, to Escalade, to CTS-V) has been extremely disappointing the way they tune them with a lot of lag on throttle input and slow power ramp for comfort. They make a 400hp+ V8 seem milder than than my ~270hp supercharged 4.0.

When doing an LS swap in a TJ, how is throttle controlled? TJ is mechanical cable and modern LS platforms are electronic (I assume?). If electronic throttle control is introduced as a result of the swap, you can install a throttle response box. I installed a Pedal Box on my 513hp BMW 750LI and it completely eliminated throttle/turbo lag (there were 9 settings). Just thinking out loud here.

 

[Fouledplugs]

When doing an LS swap in a TJ, how is throttle controlled? TJ is mechanical cable and modern LS platforms are electronic (I assume?). If electronic throttle control is introduced as a result of the swap, you can install a throttle response box. I installed a Pedal Box on my 513hp BMW 750LI and it completely eliminated throttle/turbo lag (there were 9 settings). Just thinking out loud here.

LS can be either, builder’s choice. Holley makes throttle bodies that support the LS3.

 

[Fouledplugs]

The LS3 is an obvious choice here. I like that the OEM engineers over at GM love them and pushed the GM Performance Parts folks to build some connect and cruise LS engines, to include an LS3.

I love the fact that the LS3, when purchased through GM performance, carries a 24-36 month warranty.

The only thing I do not like is the mated trans. Let me pick my own trans. I would buy just the complete engine from them and buy my trans elsewhere.

 

[toximus]

During this dreaming phase I have mulled over many different ideas from the different forums and phone conversations ranging from Hemis which would interface easier with the existing dash electronics, a high horsepower SRT8 Hemi, 1000hp turbo LS, dash ideas, cheap junkyard LS engines, different transmissions, Hellephant engines, exhaust header configurations, various wiring concerns, diesels, turbos, etc etc etc. Somebody even mentioned a '98 Honda Civic 4-banger!

To help unmuddle the mixture I got in touch with a guy who does engine swaps for a living and has worked with both the Hemi and LS, he's been kind enough to answer some questions for me and point me in the right direction.

The best advice I received is to do a proven engine swap that's been done before and not be the first to do something. Because reliability and actually getting my Jeep running sounds good to me, this seems to be advice that I'll be following throughout the entire swap even if it means missing out on something new and cool.

From the sounds of it, the LS engine is going to have the best bet of fitting into my build.

All of the Jeep interior stuff will function as long as they're powered up with 12v. The airbags, wipers, lights, turn signal, hvac blower, radio etc do not require the PCM.

If I want the factory gauge cluster to work with an LS then I will need to make a special harness that incorporates the GM side with the Jeep side PCM. However the easiest, most reliable and problem free solution will be aftermarket gauges that will interface directly with the GM ECU.

Even though I will be going with an LS I expect most of what I post about packaging the engine and trans will apply to any high uptravel builds where a high pinion axle housing travels up into the engine bay.

 

[toximus]

When doing an LS swap in a TJ, how is throttle controlled? TJ is mechanical cable and modern LS platforms are electronic (I assume?). If electronic throttle control is introduced as a result of the swap, you can install a throttle response box. I installed a Pedal Box on my 513hp BMW 750LI and it completely eliminated throttle/turbo lag (there were 9 settings). Just thinking out loud here.

My understanding is that drive by wire (electronic) is the better option for what I'll be doing since the automatic transmission talks to the engine. In theory the signal from the gas pedal to the throttle body should be able to travel near the speed of light and feel as if it's directly connected.

 

[toximus]

The LS3 is an obvious choice here. I like that the OEM engineers over at GM love them and pushed the GM Performance Parts folks to build some connect and cruise LS engines, to include an LS3.

I love the fact that the LS3, when purchased through GM performance, carries a 24-36 month warranty.

The only thing I do not like is the mated trans. Let me pick my own trans. I would buy just the complete engine from them and buy my trans elsewhere.

View attachment 167811

What transmission would you choose?

 

[Fouledplugs]

Even though I will be going with an LS I expect most of what I post about packaging the engine and trans will apply to any high uptravel builds where a high pinion axle housing travels up into the engine bay.

Holley makes a very low profile engine pan.

The Camaro exhaust manifolds, the Holley LS swap headers, and the hooker ls swap manifolds play nice with the narrow TJ frames.

some folks have had good luck with Sanderson swap shorties. But I am not a fan of them.

 

[taylormade73]

My understanding is that drive by wire (electronic) is the better option for what I'll be doing since the automatic transmission talks to the engine. In theory the signal from the gas pedal to the throttle body should be able to travel near the speed of light and feel as if it's directly connected.

True, but actual throttle response depends on how throttle response is programmed. Mine, and any factory BMW ive driven, had severe throttle lag even though it is electronic necause they come programmed that way. Thus, the aftermarket support for throttle response boxes that eliminate the lag. They plug in between the pedal and throttle body. My Pedal Box on my 513hp 750 made that HP feel instantaneous. I believe there are some for newer Jeeps as well called "Pedal Commanders."

 

[toximus]

Holley makes a very low profile engine pan.

The Camaro exhaust manifolds, the Holley LS swap headers, and the hooker ls swap manifolds play nice with the narrow TJ frames.

some folks have had good luck with Sanderson swap shorties. But I am not a fan of them.
View attachment 167875View attachment 167876

Do you know how the CTS-V headers compare?

 

[Fouledplugs]

Do you know how the CTS-V headers compare?

I have not read anything about them? You?

 

[Fouledplugs]

Even though I will be going with an LS I expect most of what I post about packaging the engine and trans will apply to any high uptravel builds where a high pinion axle housing travels up into the engine bay.

@Chris has done a lot of research on this. To the point he was fully invested and his end goal was a LS purchase. I think he would agree, the LS3 is one of the best bangs for your buck when it comes to LS swapping a rock crawler. Factory Jeep? GM 4.8 or the GM 5.3 is great. Anything more and I would advocate for something more like 6.0 or LS2/3.

The LS3 has a proven track record when it comes to the hot rod/restomod community, to include Jeeps. It’s the new “LS1,” for sure.

I got lucky and scored a smoking deal on an LQ9 6.0L.

 

[toximus]

I have not read anything about them? You?

As far as OEM goes, they seem to give the best driveshaft clearance. I haven't looked into the aftermarket options though.

 

[Chris]

@Chris has done a lot of research on this. To the point he was fully invested and his end goal was a LS purchase. I think he would agree, the LS3 is one of the best bangs for your buck when it comes to LS swapping a rock crawler. Factory Jeep? GM 4.8 or the GM 5.3 is great. Anything more and I would advocate for something more like 6.0 or LS2/3.

The LS3 has a proven track record when it comes to the hot rod/restomod community, to include Jeeps. It’s the new “LS1,” for sure.

I got lucky and scored a smoking deal on an LQ9 6.0L.

Absolutely. If I was going to pick any LS engine it would be an LS3. Sure there are higher HP versions out there, but with 426 HP and ease of availability, the LS3 is a great choice.

 

[Fouledplugs]

What transmission would you choose?

Hands down, the 4L80E.

I have yet to snap any pics, the crate just delivered yesterday. In regards to my current YJ rock crawler build, I opted for a built 4L80E from the expert builder/owner over at Maximum Transmission in California. Outstanding customer support. His wife runs the front desk and he will get on the phone with you with any question or concern. Very transparent.

https://maximumtransmissions.com/

He mainly builds transmissions specifically for Ultra4 guys and trophy truck guys. Do a little research and you will see the 4L80E and 6L80E is far more worth it when in a rock crawler and compared to a 4L60E. Note: the 6L80E has some awesome features including a great 1s gear ratio. But it is very pricey, still somewhat new to aftermarket support, and not the smallest trans to try and squeeze into a TJ/LJ.

Bottom line, the 4L60E is tough to keep alive even when built. You will find that a lot of reputable transmissions shops/builders wont even build 4L60E’s. Instead most build the very proven 4L80E.

 

[Fouledplugs]

As far as OEM goes, they seem to give the best driveshaft clearance. I haven't looked into the aftermarket options though.

I do like OEM. Ill look into them.

 

[toximus]

I made my mind up!

I chose to go with a V8 Chevy LS3 6.2L 495hp crate engine. If I ever want more power I can top it off with a Maggie supercharger to make somewhere around 630hp on pump gas or build up the internals to make more power naturally aspirated. If it's too much power I can replace the hot cam with the regular cam to make 430hp.

How I chose this horsepower is the equation that more horsepower = more better. ...at least up to a point... At some point there is a $/HP wall that's expensive and with cheaper power adding mods you run the risk of pushing the engine too far and causing reliability issues. I also have concerns of the throttle being too touchy for slow speed crawling or accidentally spinning the tires on the highway. When you take into account the power to weight ratio of my Jeep and the power required to rotate the 37" tires I think 495hp will start to balance out nicely. My power to weight ratio will be about 1hp:9lbs. In comparison a stock TJ has a ratio of 1hp:18lbs, a 2dr JL is 1:14, a Ford Raptor is 1:12, a Polaris RZR turbo is 1:11, a sports car or top model Jeep STR8 is in the 1:7 range. With my deep 5.38 gears in the axle I probably won't be winning any 1/4 miles but real world driving should be excellent on road and off road.

I did not go with the 530hp crate engine with the ASA cam because the hp/tq chart shows that more power is created at the higher rpms and not as much at the low end like the 430hp and 495hp crate engines do which isn't ideal for me. The lopey cam sounds awesome with good chop but I don't want to have trouble with a low idle either.

The other runner up I considered is the LSX 454. It has 130hp more than the LS3 I chose at the cost of being 150lbs heavier due to having an iron block. In the end I had concerns that it'd have too much power and act more like an on/off switch than incremental throttle, that would only be fun until the first road trip...

I ended up deciding on the crate engine vs junk yard after looking at various used options and finding that the good low mile stuff went before I could nab it. With the crate engine I won't have to worry about preexisting issues, damaged parts, or having to mix and match the best of different stuff together to make the engine the way I want it. From what I've researched mixing and matching different electronic bits from different models and years can also cause electrical connector confusion and ECU reprogramming. Since I'm not familiar with the LS platform that sounded like more than I am willing to take on. What isn't great about the crate engine is that it's not complete and I'm going to have to figure out what's "missing" and finish off the engine.

The LS3 engine is made from aluminum and weighs approximately 100lbs less than the Jeep 4.0L that's coming out. So that's pretty cool!