LT engine swap questions

M0J0

Member
I have been doing research. I live at high elevation and lose 1/3rd of my HP. I have decided to do a gen V swap. I am running a fully built rig with PR60/80 and 40s. The 8L90 will help a bunch with the mountains. Right now it is dreadful. I am debating between three engines. LT4, L86, and L86 w/ Texas Speed cam swap. My budget is flexible, but not infinite. Is the LT4 HP overkill even at altitude? What is a good price for a low mileage LT4 and L86? Is the Atlas 4 worth the extra money over a 2?
 
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M0J0

Member
LT4 or LT1/Atlas II/8L90e

I am going to have Motec do the install in Jan/Feb of next year. That is prime snow for time and no place to be driving my rig. Robbie said they will have their LT4 kit ready around October. I will make the decision closer to then. The decision between LT4/1 will depend on how much money I make this year. What price I can locate a LT4 and the miles. If I want to do a used or new LT1. Once, I am at 30K an extra 5-6K for the LT4 is not making or breaking my life. This is for brand new. 650hp up here is only 425hp, so I am shooting for the LT4. The reasoning behind the LT1 is there is a lot of aftermarket support now if it is not enough power. I will decide next winter. BTW, we have the same setup. The stock engine can't cut at altitude. I get passed by semis on I70.
 
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bhaner

Active Member
From what I read the LT1 and L86 are the same engine outside of the accessories and intake.

Motec told me at one point the L86 was easier to fit because of that.

I did like the idea of the LT4 with dry sump.... But $$$$


I haven't been over 3k ft since my build. I know it does well at 0-1000 ft. I am able to go over 80 on the freeway with a decent grade. I would bet it sucks at anything higher.
 
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M0J0

Member
The LT4 comes with a dry and wet sump depending. It is overkill for you. Basically, a LT4 at my elevation is a LT1 for you. I would not bother with a swap if I lived at your elevation.
 

bhaner

Active Member
The LT4 comes with a dry and wet sump depending. It is overkill for you. Basically, a LT4 at my elevation is a LT1 for you. I would not bother with a swap if I lived at your elevation.

Yep. Overkill for here. But I do plan to drive at higher elevations on a few trips. Colorado being one of them.
 

M0J0

Member
For a trip you can live with it fine. Once you are in low it does not matter. I would save the 20K.
 

Irish JK

Caught the Bug
Not to be a buzzkill, but you’re still running power through a transmission with a computer. I’m not an expert on the 8l90, but I believe it will “manage” power output like almost all other modern transmissions. Pretty hard to get all that power actually into the drivetrain.

Additionally, the times that it will allow the full power, pulling hills and or at elevation, you are going to have massive cooling issues to deal with if you actually drive it the way you are thinking. The LT4 is known to prone to cooling issues to begin with, then shove it in a JK engine bay.

From experience, I can tell you a stock LS3 with a 6l80 in a very heavy JK is plenty to get back comfortable drivability on climbs at elevations. So it reasons an Lt1/l86 with more tech and torque and an 8 speed would be even more than enough. From that same experience though, do be concerned with cooling. And a whole host of other issues if you plan to do any more than light wheeling.


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fiend

Caught the Bug
Not to be a buzzkill, but you’re still running power through a transmission with a computer. I’m not an expert on the 8l90, but I believe it will “manage” power output like almost all other modern transmissions. Pretty hard to get all that power actually into the drivetrain.

Additionally, the times that it will allow the full power, pulling hills and or at elevation, you are going to have massive cooling issues to deal with if you actually drive it the way you are thinking. The LT4 is known to prone to cooling issues to begin with, then shove it in a JK engine bay.

From experience, I can tell you a stock LS3 with a 6l80 in a very heavy JK is plenty to get back comfortable drivability on climbs at elevations. So it reasons an Lt1/l86 with more tech and torque and an 8 speed would be even more than enough. From that same experience though, do be concerned with cooling. And a whole host of other issues if you plan to do any more than light wheeling.


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What other issues are you alluding to?

Whenever I start getting excited about a V8 swap and momentarily justify the cost in my head and figure a scheme to disguise it from my wife, a nagging voice in my head reminds me of reliability issues I’ve seen and heard about.


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Irish JK

Caught the Bug
What other issues are you alluding to?

Whenever I start getting excited about a V8 swap and momentarily justify the cost in my head and figure a scheme to disguise it from my wife, a nagging voice in my head reminds me of reliability issues I’ve seen and heard about.


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Not sure I would call them reliability issues but rather drawbacks and constant teething issues. Especially if you don’t live in the same city as your installer.

The overheating does suck (to be fair, mine is not constant). Really makes you question the worth of the power.

Additionally, make sure to walk through all of the programming “choices” with your swamp kit installer etc. You’d be surprised at some of the settings the kits come with.


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M0J0

Member
Not to be a buzzkill, but you’re still running power through a transmission with a computer. I’m not an expert on the 8l90, but I believe it will “manage” power output like almost all other modern transmissions. Pretty hard to get all that power actually into the drivetrain.

Additionally, the times that it will allow the full power, pulling hills and or at elevation, you are going to have massive cooling issues to deal with if you actually drive it the way you are thinking. The LT4 is known to prone to cooling issues to begin with, then shove it in a JK engine bay.

From experience, I can tell you a stock LS3 with a 6l80 in a very heavy JK is plenty to get back comfortable drivability on climbs at elevations. So it reasons an Lt1/l86 with more tech and torque and an 8 speed would be even more than enough. From that same experience though, do be concerned with cooling. And a whole host of other issues if you plan to do any more than light wheeling.


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Well this is an argument with Robbie. He says he has a bunch of heavy JKs running gen V engines with the eight speed in Colorado. Feel free to call him.
 

Exodus 4x4

New member
Not sure I would call them reliability issues but rather drawbacks and constant teething issues. Especially if you don’t live in the same city as your installer.

The overheating does suck (to be fair, mine is not constant). Really makes you question the worth of the power.

Additionally, make sure to walk through all of the programming “choices” with your swamp kit installer etc. You’d be surprised at some of the settings the kits come with.


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Your cooling issues should be pretty easy to rectify. I mean, as long as the system doesn’t have any air in it then you should be able to adjust the fan tables easily enough to control the temperature. Even in heavy wheeling I’d be surprised to see anything over 200*. Obviously running the ac is going to effect that, but shouldn’t be more than 210* in that situation either. I usually set them so the fan is ALWAYS at 25%, and then slowly ramp up from there. By the time the temps start trying to push 203-205 I’ve already got the fan at 40-45%. Some will use the argument that the LS “likes” to be at 210-215*, but the problem with that is there is such a small window to control the temperature when you actually start trying to play around. We’ve also never noticed any performance differences on the dyno between those temperature ranges, so I call bullshit on that anyways.


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Irish JK

Caught the Bug
Well this is an argument with Robbie. He says he has a bunch of heavy JKs running gen V engines with the eight speed in Colorado. Feel free to call him.

Who’s arguing?? You asked for input so I responded with real world experience. Proceed however you’d like.


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OverlanderJK

Resident Smartass
Well this is an argument with Robbie. He says he has a bunch of heavy JKs running gen V engines with the eight speed in Colorado. Feel free to call him.

You came here asking for opinions, got real world experience and opinions then say people are arguing? Wtf?

You should do whatever costs more. That is a proven fact that it is more better. You seem like that type.


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