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98 Eclipse GS | LS1 Swap Help

Mitzu Garage

Proven Member
79
110
Oct 9, 2020
Indianapolis, Indiana
Please be respectful, this is very sentimental to me. I have a bunch of questions. I have a 1998 Mitsubishi Eclipse GS. I’ve been debating on what to do with it. I’m really into the 4G63 platform and have a GS-T as well already in my garage. I’ve always wanted to work on a car with my dad but he’s really not into the import scene and we can never agree on a car to work on together. He was at my place staring at the car saying it’d be cool to put a LS motor into it. I think this would be an amazing project to work on together. It would have my style with his personality under the hood. I’m not a big muscle car fan but I would love to have something we worked on together.

He has a spare LS1 motor for it and was thinking of throwing in a Ford 9 inch or 8.8 rear end. Does anyone have any good idea on how to mount the engine and rear end? I’ve seen some LS swapped Eclipses on YouTube but can’t seem to find the owners. Any leads would greatly be appreciated.

Now I don’t want to hear, “oh, you better have deep pockets, blah blah blah” My dad restores cars for a living so he is the perfect person for this project. He has all the available resources to get the job done. He doesn't have the car in his possession yet but I figured I'd so some asking around.
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BlackGSXEclipse

Proven Member
178
21
Feb 9, 2007
Maryville, Tennessee
Just keep in mind that there is a big difference in restoring cars, and doing a full custom build.
There is a reason you don’t see things like this finished out. It just does not financially make sense.
Your going to have to cut the firewall, parts of the floor for a trans tunnel, and cut out the entire rear pan and go custom mounts for everything.
Honestly it’s one of those things, if you have to ask, it’s probably not for you.
 

tlikethedrink

Proven Member
362
90
Sep 11, 2007
ABQ, New_Mexico
I respectfully agree. It would be easier and probably cheaper in the long run to find another platform that LS swap kits are made for like Miatas or 300z. Even something with an existing RWD would put your light years ahead. orherwise, your building a tube chassis and placing the body over it. Find a cheap roller and go from there. It’s a chance to add to your collection! Older RX7s, Supras, Starions, 300z, are cheap enough. Or compromise and build a Foxbody. The learning experience will be good for the next build.
Just keep in mind that there is a big difference in restoring cars, and doing a full custom build.
There is a reason you don’t see things like this finished out. It just does not financially make sense.
Your going to have to cut the firewall, parts of the floor for a trans tunnel, and cut out the entire rear pan and go custom mounts for everything.
Honestly it’s one of those things, if you have to ask, it’s probably not for you.
 

ErikTande

Supporting Member
1,468
498
Dec 17, 2012
Centennial, Colorado
^^ Yep, restoration and custom fabrication are not the same thing. The people that have done this swap likely haven't documented it online, so you'll be on your own as to figuring out the best way to cut the chassis, create the mounts and fabricate the structural reinforcement needed. It'll be an enormous project.

Take a look at this project, putting a 4g63 in a Beetle... This is about level of fabrication that will be required to get an LS in a 2g Eclipse.
https://www.dsmtuners.com/threads/4g-71-super-beetle.506033/







at 1:35 when the car takes off it, the sound it makes confuses my brain LOL

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95REGF150

Proven Member
433
219
Mar 7, 2012
Elk Grove, California
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Wow had not seen that car before thanks for sharing. Always wondered how you would deal with the steering if you went RWD cause the rack is so far back. Well this answers that question just set the motor that far back to match. And I totally agree when it runs on the track it just seems like a movie where their using the wrong sound effects haha. Pretty unique car and very cleanly done. Really cool to watch one of these cars wheel stand.

But besides the uniqueness and not having to worry about spitting out a part of the drivetrain every pass seems like there are easier and cheaper ways to go 9's in these cars.
 

95REGF150

Proven Member
433
219
Mar 7, 2012
Elk Grove, California
OP I know you are not really getting much useful responses but that is just because everyone on this forum mostly deals in the factory engine/divetrain configuration.

But since you were looking for advice I'll try to help out as I have built a few mustangs that were drag cars. And that's really what you need for this build is a shop that does drag cars. Because in the drag racing world the eingine/drivetrain is main part of the build. You then drop it into any body that you wish and apply the same steps in doing so.

First look at universal back half frame rail kits for Mustangs, Novas, etc. like the below from S&W race cars. You will cut the whole back of the car floor out and install the frame rails using some ingenuity and a lot of welding. They have all the 4 link or ladder bar suspension points for your 8.8 or 9 inch ford rearend (cheapest options). Then you will have to remake the whole rear floor and wheel tubs using sheet metal. That will be a ton of work but done all the time in most drag cars youve seen that were RWD from the factory. SO not much more work in doing a FWD Eclipse here really. Also means you can get some big tires back there. Big as you want if you want to do full 20"+ slicks. The guy in the youtube Eclipse stayed more conservative on a small tire. Maybe to cut down on the fab work he left the upper part of the factory tubs in place and just cut out the floor for some frame rails.
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For the engine install you will have to remove the whole firewall and most of the front floor. Then you will need an LS front sump oil pan and put the hump in the pan centered directly over the front steering rack subframe in the Eclipse. Looks like that's what the guy in the video did. I'm sure he had to modify the subframe as well but at least it keeps the front suspension and steering OEM so you don't have to reinvent the wheel on that. Then it's engine mounts custom fabbed as well as trans crossmember. With the motor in place you can remake the tunnel and firewall again from a lot of sheet metal, time, and a whole lot of welding.

Now from that point you have the bones of a car again. All that's left will be everything else. Your talking pedals, brake master cylinder, steering column mount, etc. All things that were effected because there is an engine now where they used to sit from the factory. And then of course the polishing things like radiator selection, wiring harness, roll cage, we could list for days. You are talking a multi-year project that requires a ton of hours. It would be best if you have some fab skills already to take this on. But if you don't it is still doable it will probably just add to the time. And you may have to do things twice or three times to get a car that's safe if you haven't done this before.

Your dad should have many of these skills to a point. But like the other guys are saying if he is truly just a restoration shop where you are bringing stuff back to factory that's way different than building your own car from scratch which is essentially what you are doing.

So hopefully that all makes sense. Its definitely a deep pockets thing but most any car build requires money. More so though this one will be an huge time investment so be ready.
 
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randman2011

Proven Member
508
234
Feb 26, 2012
Indianapolis, Indiana
Aside from the custom fab work to make the transition from transverse FF to longitudinal FR, the big thing that comes to mind is that the Eclipse just isn't a great chassis to begin with. It's very heavy and the chassis is quite floppy relative to its contemporaries. I get that the whole back end would be redone with different suspension and the front would probably see some change as well, but the middle part isn't a great donor for a project like this. I'd suspect that the end result would find itself on a drag strip more than any track and for that you'd have to worry less about chassis reinforcement, but it's still really heavy for what it is. It would be a fun project and there have been (undocumented) conversions going back 15 years at this point, but for that much effort I would personally choose a different platform that has fewer inherent weaknesses in the chassis. For reasons that I cannot explain, a del Sol comes to mind. That would be a horrible idea and definitely under no circumstances should someone V8 RWD swap a del Sol.

EDIT: Oh hey, Jake. I missed that it was you. You should have V8 swapped your Lancer wagon instead!
 
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95REGF150

Proven Member
433
219
Mar 7, 2012
Elk Grove, California
There are some good pictures in this thread of how much cutting of the floor would be required to do what your looking for.

https://www.dsmtuners.com/threads/project-2g-rwd-conversion.441214/

Sadly this car went unfinished beyond the easy part of cutting it up which is what I think everyone is trying to warn you off from.

After watching these videos am I the only one that would like to see the 4g63 in something light, like a crx or eg hatch. Yes I know boosting a b or k motor would be easier but 4g63 would be interesting.

So weird this just got posted on the FB groups for sale today. 7 Bolt swapped Integra. Iv'e certainly never seen one before. Guy says it roasts them through 3rd on 10psi. Pretty cool build.

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Ludachris

Founder & Zookeeper
7,883
2,495
Nov 12, 2001
Newcastle, California
OP I know you are not really getting much useful responses but that is just because everyone on this forum mostly deals in the factory engine/divetrain configuration.

But since you were looking for advice I'll try to help out as I have built a few mustangs that were drag cars. And that's really what you need for this build is a shop that does drag cars. Because in the drag racing world the eingine/drivetrain is main part of the build. You then drop it into any body that you wish and apply the same steps in doing so.

First look at universal back half frame rail kits for Mustangs, Novas, etc. like the below from S&W race cars. You will cut the whole back of the car floor out and install the frame rails using some ingenuity and a lot of welding. They have all the 4 link or ladder bar suspension points for your 8.8 or 9 inch ford rearend (cheapest options). Then you will have to remake the whole rear floor and wheel tubs using sheet metal. That will be a ton of work but done all the time in most drag cars youve seen that were RWD from the factory. SO not much more work in doing a FWD Eclipse here really. Also means you can get some big tires back there. Big as you want if you want to do full 20"+ slicks. The guy in the youtube Eclipse stayed more conservative on a small tire. Maybe to cut down on the fab work he left the upper part of the factory tubs in place and just cut out the floor for some frame rails.
You must be logged in to view this image or video.


For the engine install you will have to remove the whole firewall and most of the front floor. Then you will need an LS front sump oil pan and put the hump in the pan centered directly over the front steering rack subframe in the Eclipse. Looks like that's what the guy in the video did. I'm sure he had to modify the subframe as well but at least it keeps the front suspension and steering OEM so you don't have to reinvent the wheel on that. Then it's engine mounts custom fabbed as well as trans crossmember. With the motor in place you can remake the tunnel and firewall again from a lot of sheet metal, time, and a whole lot of welding.

Now from that point you have the bones of a car again. All that's left will be everything else. Your talking pedals, brake master cylinder, steering column mount, etc. All things that were effected because there is an engine now where they used to sit from the factory. And then of course the polishing things like radiator selection, wiring harness, roll cage, we could list for days. You are talking a multi-year project that requires a ton of hours. It would be best if you have some fab skills already to take this on. But if you don't it is still doable it will probably just add to the time. And you may have to do things twice or three times to get a car that's safe if you haven't done this before.

Your dad should have many of these skills to a point. But like the other guys are saying if he is truly just a restoration shop where you are bringing stuff back to factory that's way different than building your own car from scratch which is essentially what you are doing.

So hopefully that all makes sense. Its definitely a deep pockets thing but most any car build requires money. More so though this one will be an huge time investment so be ready.
This is probably the best advice you can get. It's going to take a massive amount of fabrication and engineering expertise to make it happen - and money obviously. The reason you won't find this documented is because it's not easy to do, it's expensive, and there isn't much upside (the allure of the DSM usually revolves around the 4G63 powerplant). In the DSM world, most people are looking for ways to go fast cheap and easy. It's cool to see huge budget builds with big horsepower and low E/Ts, but the vast majority are working with a shoestring budget.

Hopefully you'll document the project here so we can all follow along. Post lots of pics and videos in your build thread please!
 

Team busby

Probationary Member
1
0
Oct 24, 2020
pima, Arizona
If your father has the skills ,money and desire the best way is a total tube chasi with a full cage most will. That will require removing most of floor and address handling and flex issues. If you do this build please post lots of photos thank you.
 

Dsmhuman

Probationary Member
26
5
Sep 12, 2019
Vancouver, Washington
If it’s a gs you already have rear wheel disks, if you guys want a good eclipse project, you could swap in a 4g64 from a 3g and stroke it out with some forged internals and a big turbo. Wouldn’t require as much fab as a v8, From there you can go the next step and adapt in a awd rear end with an evo tyranny and go awd turbo stroker. The car will retain a solid weight distribution and could potentially quadruple the power output from your stock motor. If you wanted to, you could probably do something with the trans to make it only send power to the back wheels.
 

Jays99Spyder

Proven Member
165
57
Feb 22, 2020
Waukegan, Illinois
If it’s a gs you already have rear wheel disks, if you guys want a good eclipse project, you could swap in a 4g64 from a 3g and stroke it out with some forged internals and a big turbo. Wouldn’t require as much fab as a v8, From there you can go the next step and adapt in a awd rear end with an evo tyranny and go awd turbo stroker. The car will retain a solid weight distribution and could potentially quadruple the power output from your stock motor. If you wanted to, you could probably do something with the trans to make it only send power to the back wheels.
Does the 64 sit different in a 3g as it does in a 2g, I only ask because in a 2g it sits the same as a 63
 

Dsmhuman

Probationary Member
26
5
Sep 12, 2019
Vancouver, Washington
Yes, it sits with the same orientation as the 420a and the evo 4-9 4g63. People use the 3g manual trans to adapt evo engines into 2g’s FWD. I’ve heard the evo engine bolts right into a 420a chassis (not counting the trans) I can’t say for sure, but I do have some suspicions that it would be the same for the 3g 4g64. You might need to do some modification and fab to mount and clearance the trans. But the engines seem to be a dime a dozen and can give some good low end power if you build right.

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Jays99Spyder

Proven Member
165
57
Feb 22, 2020
Waukegan, Illinois
Yes, it sits with the same orientation as the 420a and the evo 4-9 4g63. People use the 3g manual trans to adapt evo engines into 2g’s FWD. I’ve heard the evo engine bolts right into a 420a chassis (not counting the trans) I can’t say for sure, but I do have some suspicions that it would be the same for the 3g 4g64. You might need to do some modification and fab to mount and clearance the trans. But the engines seem to be a dime a dozen and can give some good low end power if you build right.
Interesting wonder if there are any 3g evo swaps out there.
 

DSMPT

DSM Wiseman
1,971
1,524
Jun 12, 2014
Japan / Mexico, Arizona
There is a V8 swap 2G Eclipse for sale in my local in Mexico. It has been sitting for some years in the owner's junk yard next my garage. I saw this was running about 10 years ago, I don't know if it's in a running condition now though. I don't know if this can be imported to the US again because I think this Eclipse is already imported to Mexico, but it's cheap anyways.
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95REGF150

Proven Member
433
219
Mar 7, 2012
Elk Grove, California
Guy had plenty of Chevy parts laying around. Look at that master cylinder reservoir. Right out of any 90's chevy truck. Radiator setup too.

Wonder if you could get by with a 3000GT rear diff and upgraded axles so you didn't have to cut up the whole rear end for a straight axle?
 

Mitzu Garage

Proven Member
79
110
Oct 9, 2020
Indianapolis, Indiana
Just wanted to tell everyone we finished the swap! Car is drivable and it’s pretty freakin’ awesome. Still have some final touches to fix this winter but WE DID IT!

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