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My 98 subaru outback jumped time again in june. I didnt want to rebuild The stock 2.5 engine because it was over 250 thousand miles and was very underpowered. But didn't want to get rid of the car because I dumped 3 grand into it last September when I installed new struts and springs for a 2004 Forrester. New brake pads calipers and rotors front and rear. New wheel bearings inner and outer tie rods ball joints e-brakes New 225 70 r15 general grabber tires on neon rims with special wide based acorn shaped lugnuts. All those new parts have less than 10 thousand miles on them and I have a personal attachment to this car so I couldn't get rid of her. A v8 swap would be very easy if I were to make it rear wheel drive but I do a lot of off-roading and I leave for work before plows come thru in the winter so I need to keep awd plus it would be stupid to have a lifted subaru 2wd. Problem keeping it awd is the engine sits in front of the front axle so that severely limits engine space. And sucks hanging the weight so far forward but the ls4 is an aluminum block and fully dressed and full of fluids is less than 600 pounds so only about 100-150 more than the 2.5

 

From bell housing to core support on the subaru is only 23 inches but to the edge of grill end of hood it is 29 inches from bellhousing. Inner frame rail side to side there is 32 inches from crank Center to highest point of the 2.5 (which is top of my msd coil) it's 11 inches from crank Center to bottom of hood about 14 inches (was hard to measure)

 

A ls4 v8 is about 24.5 inches long from bellhousing to front of accessories so I would have to get a narrow radiator with slim electric fans and move it and the core support all the way forward to the edge of the hood and make a custom mesh grill. But that should be enough to make it fit

 

Ls4 crank shaft Center up is 15.5 inches. A 2 inch spacer lift kit is 450 with shipping and I have been wanting to do one since I put Forrester struts and springs in the car. Not to lift it anymore it's the perfect height how it is. i want the spacer kit to lower the subframe down to get cv angles better and to get the alignment back to stock. caster and camber are slightly off got close as possible last time I aligned it but couldn't get it perfect. Plus rear tires sit slightly forward right now. So a 2 inch spacer kit will fix all that plus should get just enough room for the ls4 to clear the hood.

 

Crank shaft to bottom of oil pan is 7 inches on the ls4 10 inches on the subaru 2.5 any ls oil pan will bolt on so finding an oil pan that clears crossmember should be easy.

Width is about 26inches so plenty of room there. it will be a tight squeeze but seems doable.

 

The ls4 uses the gm small metric bellhousing pattern that most front wheel drive gm cars use. And is relatively easy to make an adapter to a subaru trans. Just need to figure out adapter thickness based on how far flywheel face is from bellhousing mounting surface on the ls4 and the 2.5. Clutch will probably be custom made by someone like spec

 

Ls4s don't have starter mounts cast into them there starter bolts to the bellhousing but so do subarus so I will us a subaru starter just need to find a 124 tooth flywheel for an ls motor so far I haven't found one.

 

Wiring can get a universal ls swap harness from painless and a pcm from a ls4 car. Most of my stock gauges don't work anyway so will have to make custom cluster with after market gauges.

 

Tune the ls4 car pcm to delete all security systems, transmission codes, displacement on demand and modify the tune for other engine mods like intake cam larger throttle body turbo etc. when they plug into the obd2 port it will think it's an ls4 gm car. As long as moniters have set and Check engine light is not on it will pass inspection.

 

I will keep all emissions components functional.

 

The ls4 has displacement on demand that shuts off 4 cylinders when cruising that system can't work with a standard tranny so will need to delete it there are kits for that and will need a new cam because of that.

 

I will swap in a ls2 intake manifold and throttle body much better air flow and I will keep it pointing towards the back like subaru stock intake I want to do a top mount sti intercooler setup with a turbo still need to look into that. Larger injectors and 6.0 truck coils. Ls motors use drive by wire electric throttle so will need a throttle pedal and throttle control module probably get one for a 2002ish corvette.

 

There is a bunch of six speed r180 swap threads so I know that can be done and I want to keep the dccd system spec b axles and drive shafts I want to keep stock hubs so I can keep the neon rims they look good and have the back spacing I need for the big tires.

 

Ls4s can be bought for around 6 or 7 hundred, 6 speed and parts are around 2500 to 4000, spacer lift kit 450, painless harness 750, ls2 intake coils throttle body 200-400, tuning the pcm costs 200-400, custom clutch and flywheel will probably be about 1000, exhaust turbo etc around 2000 should be able to do it all for around 10 to 15 thousand which ain't bad. Right now still watching for good deals on motor and tranny and stuff. And trying to plan it all out. And while the car is down I want to finally do rust repair and while I got the core support all cut out and being moved forward I want to strengthen all that area and build a winch bumper. And extend rear quarters down and build a rear bumper and replace rockers with thick steel plate for body protection and a place to attach subframe connectors. Rust repair bumpers rockers subframe bracing were my plans for it this winter but now that the motor died this project is a lot bigger and all my other project cars are on hold till the subie is done.

Edited by 87bluebird
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With all that work and that cost, why not just convert it to a sti motor. Less Coss and a lot less work. With the Mk ry you save you could build the motor to about 400 HP or more. A company in Spokane does a 600+ HP sti build for about 7k.

 

Just a thought

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A full sti swap was my original plan but everything to do a full sti swap will come to almost 10 thousand. So not much less. And if I spent another 5-7 thousand to get it around 600 horsepower I will be about at the limits of what power you can get out of it, while keeping it reliable enough for daily driving. A ls4 with a mild cam ls2 intake throttle body and coils larger injectors a single turbo making 7 to 10 pounds of boost can easily hit 5-6 hundred horsepower and can easily be given future Upgrades to get closer to 800-1000 horsepower and still be kept reliable. Only thing that's really extra work doing the v8 instead of sti swap is moving the radiator and core support forward and building custom motor mounts and custom exhaust. But those 3 things are very easy to do. Also ls motors have a ton of after market support and parts for them are relatively cheap. sti swaps have been done before a v8 swap while keeping awd has never been done before. A couple of people have done v6 swaps in newer subaru legacys and kept awd I thought about doing the same and stuffing a l67 in the subaru I even measured the motor in my 07 grand prix but those v6s are around the same length as the ls4 but the l67 slightly taller because of the supercharger. L67 vs ls4 bout same cost and amount of work but can get more power out of a v8.

Edited by 87bluebird
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Not saying I want to make it 1000 horsepower 600-700 with awd in a car that weighs about 3500 pounds will be a lot of fun and it's nice to know your not pushing the engines limits to get that power. And that I can easily get more out of it if I ever get bored with it.

Edited by 87bluebird
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  • 1 month later...

Any progress with this?  I like the idea of a few inches of body lift and moving the rad forward to fit the LS V8.

 

Another option would be an H6 swap, there is at least one company that makes a supercharger kit to make 400 easy hp, I'm sure it can be cranked up from there if you really need it.  Haven't watched it all, but Might Car Mods did an H6 swap into a Legacy/Outback and got into the 11s.

 

I would recommend buying a rust free car and putting everything into that, especially if you're going to spend 10-15k building this thing up.

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