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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="elgordo371" data-source="post: 460964" data-attributes="member: 25539"><p>If you stroke the 4.0, put a performance camshaft in it, and use newer fuel injectors you will be running about 230-240HP and over 300 ft-lbs torque. Your horsepower loss relative to a 3.6 or 3.8 will be theoretical as it will be in the 4000-5500 rpm range where you almost never go in most driving, and even wheeling scenarios. Meanwhile you gain some torque from 1500-3000 RPM. You will need to use the 4.0 computer and instrument cluster appropriate to your engine/transmission pairing.</p><p></p><p>Or you could maybe let a holley sniper control the EFI and cluster...</p><p></p><p>If you have a manual tranny, then your engineering problem is to mate the 4.0 to the transmission. If its the NSG 6-speed it can be done. Just use the computer from a 4.0 with a manual.</p><p>If you want an auto transmission then you'll have to find/get a discrete trans computer for it, and integrate it with the ECU yourself.</p><p></p><p>I don't think this would be worth doing with a 2000-2006 4.0. The ignition is too specialized, and the rest of the engine too prone to bad castings and other defects. </p><p></p><p>But if you use a good '92-'98 4.0 then parts are generic, plentiful, and inexpensive. If you are a "keep my Jeep FOREVER kinda guy this is a viable route.</p><p>The 4.0 shines in longevity and rebuildability. If you stroke it, the compression will rise. You will need 89 octane gas. And you will lose some of the longevity...but not the repairability.</p><p>With that setup you could get 200,000-300,000 on the first motor, and then just pop another identical motor in, and get another 200-300k miles.</p></blockquote><p></p>
[QUOTE="elgordo371, post: 460964, member: 25539"] If you stroke the 4.0, put a performance camshaft in it, and use newer fuel injectors you will be running about 230-240HP and over 300 ft-lbs torque. Your horsepower loss relative to a 3.6 or 3.8 will be theoretical as it will be in the 4000-5500 rpm range where you almost never go in most driving, and even wheeling scenarios. Meanwhile you gain some torque from 1500-3000 RPM. You will need to use the 4.0 computer and instrument cluster appropriate to your engine/transmission pairing. Or you could maybe let a holley sniper control the EFI and cluster... If you have a manual tranny, then your engineering problem is to mate the 4.0 to the transmission. If its the NSG 6-speed it can be done. Just use the computer from a 4.0 with a manual. If you want an auto transmission then you'll have to find/get a discrete trans computer for it, and integrate it with the ECU yourself. I don't think this would be worth doing with a 2000-2006 4.0. The ignition is too specialized, and the rest of the engine too prone to bad castings and other defects. But if you use a good '92-'98 4.0 then parts are generic, plentiful, and inexpensive. If you are a "keep my Jeep FOREVER kinda guy this is a viable route. The 4.0 shines in longevity and rebuildability. If you stroke it, the compression will rise. You will need 89 octane gas. And you will lose some of the longevity...but not the repairability. With that setup you could get 200,000-300,000 on the first motor, and then just pop another identical motor in, and get another 200-300k miles. [/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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