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Jeep Wrangler JK
JK General Discussion
JK 3.8 swap to a 4.0 how to?
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<blockquote data-quote="Dirty Dog" data-source="post: 452086" data-attributes="member: 24042"><p>I do not recall ever hearing about anybody doing this particular swap. Probably because there really isn't a good reason to do it. </p><p></p><p>You would need to fabricate your own mounts, which admittedly isn't super difficult. There is a good chance that fitment issues will mean fabricating your own oil pan, steering components, etc. You're going to need the ECU from a TJ as well as the engine. You will quite possibly need other modules as well. The transmission should bolt up, but the 42RLE is controlled by the ECU. The one you just took out so you could use the TJ ECU... </p><p></p><p>I'm sure there's more. The point is, you've never done an engine swap, and this will be a very complicated engine swap. And for what?</p><p>[ATTACH]122642[/ATTACH] [ATTACH]122643[/ATTACH]</p><p></p><p>I stole the 4.0L dyno numbers from Motortrend. It had a CAI, header, and exhaust, so it's a tiny bit higher than stock. </p><p></p><p>So you're considering a nightmare swap for a net loss in usable power.</p><p></p><p>It would be easier and cheaper to do a Hemi swap. And even easier and cheaper to do an LS swap.</p><p>[ATTACH]122645[/ATTACH]</p><p>This is the dyno sheet from my Vette. The lower numbers are a basically stock LS1 with a CAI, long tube headers, high flow cats, and a Magnaflow exhaust.</p><p>The top numbers are from the Heads/Cam/Blower LS3 that was swapped in. That engine is currently out. We're install a forged crank, billet rods, and forged pistons. Lowering the static CR from 10.7:1 to 10:1 so we can run a bit more boost and timing. </p><p></p><p>A stock LS1 would give you a torque curve that is nearly as flat as a table, with over 300lb/ft @ 2400 RPM. </p><p></p><p>If your buddy wants a swap, it just makes sense to either do the simple swap (3.8 to 3.8) or a swap that will provide an improvement in performance (Hemi or LS1). You're still looking at swapping things like the ECU and transmission, but aftermarket support for these swaps is huge, which means someone else already figured out the HOW.</p></blockquote><p></p>
[QUOTE="Dirty Dog, post: 452086, member: 24042"] I do not recall ever hearing about anybody doing this particular swap. Probably because there really isn't a good reason to do it. You would need to fabricate your own mounts, which admittedly isn't super difficult. There is a good chance that fitment issues will mean fabricating your own oil pan, steering components, etc. You're going to need the ECU from a TJ as well as the engine. You will quite possibly need other modules as well. The transmission should bolt up, but the 42RLE is controlled by the ECU. The one you just took out so you could use the TJ ECU... I'm sure there's more. The point is, you've never done an engine swap, and this will be a very complicated engine swap. And for what? [ATTACH]122642[/ATTACH] [ATTACH]122643[/ATTACH] I stole the 4.0L dyno numbers from Motortrend. It had a CAI, header, and exhaust, so it's a tiny bit higher than stock. So you're considering a nightmare swap for a net loss in usable power. It would be easier and cheaper to do a Hemi swap. And even easier and cheaper to do an LS swap. [ATTACH]122645[/ATTACH] This is the dyno sheet from my Vette. The lower numbers are a basically stock LS1 with a CAI, long tube headers, high flow cats, and a Magnaflow exhaust. The top numbers are from the Heads/Cam/Blower LS3 that was swapped in. That engine is currently out. We're install a forged crank, billet rods, and forged pistons. Lowering the static CR from 10.7:1 to 10:1 so we can run a bit more boost and timing. A stock LS1 would give you a torque curve that is nearly as flat as a table, with over 300lb/ft @ 2400 RPM. If your buddy wants a swap, it just makes sense to either do the simple swap (3.8 to 3.8) or a swap that will provide an improvement in performance (Hemi or LS1). You're still looking at swapping things like the ECU and transmission, but aftermarket support for these swaps is huge, which means someone else already figured out the HOW. [/QUOTE]
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Jeep Wrangler JK
JK General Discussion
JK 3.8 swap to a 4.0 how to?
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