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

Since you don't get a lot of replies in here, thanks for all the documentation and pictures.:smokin:

It's so much info and I've been paying attention for when I get around to my budget version for the TJ. :homer:

Thanks for the kind words! It's always nice to have somebody chime in every now and again. I've noticed that this thread gets a ton of views but not many posts.

You've probably figured it out, but there are ways to keep the budget lower without compromising the build. A known good 250-300hp LS junkyard engine would help reduce the cost significantly not only because the engine would be cheaper to start with but because you could get by with other lower cost components (stock JK transferase, cheaper 1310 driveshafts, cheaper axles, etc). If you don't mind a 4L instead of the 6L80 you can save some money there too since the wiring hardness would be much more doable to splice yourself instead of having to have a CANBUS interface like I had to do.
 
Thanks for the kind words! It's always nice to have somebody chime in every now and again. I've noticed that this thread gets a ton of views but not many posts.

You've probably figured it out, but there are ways to keep the budget lower without compromising the build. A known good 250-300hp LS junkyard engine would help reduce the cost significantly not only because the engine would be cheaper to start with but because you could get by with other lower cost components (stock JK transferase, cheaper 1310 driveshafts, cheaper axles, etc). If you don't mind a 4L instead of the 6L80 you can save some money there too since the wiring hardness would be much more doable to splice yourself instead of having to have a CANBUS interface like I had to do.

I did pickup a van and started getting to pulling the 6.0 LQ4 and 4L80 last night. TJ already has a Atlas and I did SD60/Sterling last year.
 
It's settled. I'm swapping the front output on the Atlas to a drive flange and sending the front 1350 driveshaft back to Tom Woods to be modified. The flange should fit no problem, but since it'll move the CV forward slightly (effectively shortening the front shaft slightly) I might need to hammer the tub a little more.

I really think a 1310 would survive up front, and there's plenty of examples of similar builds with that being the case. 450hp seems to be roughly the tipping point where Tom Woods suggests going to a 1350 joint in the front. There's other factors too like tire size and differential gearing. I noticed this similar tipping point when I bought the 6L80e transmission and Atlas where they wanted to beef up components that I wouldn't have had to with less power. My argument to go with the stronger parts is that it's not negatively affecting my build and if things get rowdy on the trail the failure point is likely going to be from denting the tube and not from shock loading a joint.

I think it's awesome that I haven't had to compromise on the high travel I worked so hard to get in phase 1 of my build and instead am actually able to use a full 2" driveshaft instead of the 1.25" shaft I was previously stuck with.
 
Another 15 page quiet reader here.

I have a job that attention to details is a must for success. Failure happens when those details are missed.
I would judge you to be on the success side easily.

Great build and thread from another LJ owner.
 
Another 15 page quiet reader here.

I have a job that attention to details is a must for success. Failure happens when those details are missed.
I would judge you to be on the success side easily.

Great build and thread from another LJ owner.

It's good to have you along for the build too! Thanks for saying hi!
 
I was asked about a few parts in PM so I figured I'd share here for everyone.

Something I always try to keep in mind is parts availability in remote areas and being able to service my Jeep if something breaks during a trip.

It was pointed out that I used 12pt ARP fasteners around my engine instead of 6pt. I don't plan to carry 12pt sockets aside from a single 1/2" 12pt socket for my steering so I can replace a heim if needed. My reasoning why this isn't a concern is that every part that is held on with a 12pt fastener is one that I either can't imagine ever servicing on a trail (like decoupling my transmission) or because I'd have to go to a parts store to order a replacement anyway so buying a 12pt socket at the same time from the parts store wouldn't add any time or hassle (such as replacing the water pump).

Parts that would likely be on a parts store shelf like a new alternator are held on with 6pt fasteners.

Speaking of the alternator, I forgot to mention it when I was talking about the accessory drive. It is a GM truck application alternator so I can replace it with any commonly available unit. This one is made by Mechman to deliver 197 amps when the engine is at 800rpm (my engine will idle around 500rpm so this number will be a bit lower) and 256 amps at 1800rpm. I opted for this higher than stock output because I'll be running electric fans and winching. Mechman tests each one before shipping.

20210128_alternator-specs.jpg
 
To get the transmission crossmember to line up perfectly with the tabs off the frame I drilled them in place to 3/8":

20210127_drilling-crossmember-tabs.jpg


20210128_transmission-crossmember.jpg


Preview of the flat belly! :)

20210128_flat-belly-skid-test-fit.jpg
 
I think I found the perfect belt length of 86.6". Continental 4060686. Application is an early 1990s Volvo 850.

20210214_belt-wrap.jpg


20210214_automatic-tensioner.jpg
 
My god..... it’s like the body was heated up and molded perfectly to that atlas/tranny..... your attention to detail is insane!! You must dream of this thing at night!!!
I enjoy the updates!!!
 
My god..... it’s like the body was heated up and molded perfectly to that atlas/tranny..... your attention to detail is insane!! You must dream of this thing at night!!!
I enjoy the updates!!!

Haha! Thanks! I do dream of it. Unfortunately work and some life things have me terribly distracted lately to the point that putting a belt on the engine feels like progress. All of that work/life stuff is going in the right direction (with a lot of hard work) and is looking to be over soon. I'm currently owed something like 30 days off at work. So more Jeep time is coming soon.
 
I run the mechman 370 amp alternator on my ls in my xj. They make some really nice stuff.
 
Notching the 3/8" 6061 belly skid around the transmission pan:

20210128_tracing_skid.jpg


20210128_cutting-skid-around-trans.jpg


20210128_test-fit.jpg


Scribing for cutting off the sides:

20210513_scribe-ends.jpg


I wanted a little more wiggle room around the transmission:

20210513_more-clearancing.jpg


Countersunk 1/2" flat head bolts for the skid. And the plasma cutter made quick work of cutting the extra on the sides off followed up with a flap disc.

20210513_recessing-heads.jpg
 
Are you planning to put any stiffening ribs on the alum skid?

I'll be putting a stiffener in the rear and the transmission crossmember acts as the stiffener in the front. I was going to use a 1/4" thick aluminum angle right along the back but with the driveshaft and exhaust I think I'd have to cut the profile too low to provide enough support. I'm waiting once my exhaust is in, but I'll likely use 1-1/4" DOM and make little feet to bolt down to the skid.


20210605_belly-stiffener-foot.jpg


20210605_belly-brace.jpg
 
Mocking up the 5/16" 7075-T6 engine skid. I went with 7075 here because it's a little stronger than 6061 and my hope is that it might prevent more oil pan damage.

20210509_mockup-engine-skid.jpg


Leaving a gap so the skid can move up when hit:

20210507_trans-skid-gap.jpg


Cutting a spacer out of 5/8" aluminum:

20210515_engine-skid-spacer.jpg
 
Trying out a different transmission line. I think this might be the best so far (cheapest too). GM #92236244.

20210515_6l80e-transmission-fluid-line-bottom.jpg


20210509_6l80e-transmission-line-side.jpg
 
So that I could cycle the front to test clearance to the new skid fully I decided to bolt the driveshaft in.

Just getting the Atlas shifters in enough to shift out of neutral so I can torque the output flange using the transmission as a brake. I also replaced both axle yokes to the 1350 yokes while I was at it.

Tom Woods sold me the flange and seal which they sourced from Advance Adapters.

20210519_test-atlas-shifters.jpg


20210519_atlas-2-output-seal.jpg


20210605_atlas-2-flange.jpg
 
I mocked up the steering to see what needs to happen. I'll wait to finish up once the engine is out again.

20210517_steering-mockup.jpg


20210517_steering-mockup-side.jpg
 
20210517_engine-skid-shoe.jpg


20210529_tabs.jpg


I bent 3/8"x1" flat bar for the left side brace over top of the control arm.

20210529_driver-side-brace.jpg
 
To fit the AC in I had to move the battery far outboard. The positive terminal now nearly touches the fender so I ordered a reverse terminal battery.

20210603_battery-ac.jpg


20210603_ac-mount-bracket.jpg


20210603_relocated-ac.jpg


20210603_ac-ls3-clearance.jpg
 
Is that the ac dryer right next to the exhaust manifold? I was about to do the same thing on my build. Apparently, it's a bad idea. The freon going through it has just come out of the condenser after being cooled. Any heat that gets put into it at that point reduces the efficiency of the system.
 
Is that the ac dryer right next to the exhaust manifold? I was about to do the same thing on my build. Apparently, it's a bad idea. The freon going through it has just come out of the condenser after being cooled. Any heat that gets put into it at that point reduces the efficiency of the system.

Yes it is. My only other option is to place the battery behind the center console to move the dryer over. So I think it's worth a try and if the AC comes out too warm I'll place a shield on it or redo.
 
Marking where the firewall needs to be clearanced with a hammer:

20210605_engine-firewall.jpg


20210605_engine-removed.jpg



20210606_hammered-filewall.jpg
 
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