Engine Engine Swap Between CJ7 and YJ Question

Engine Engine Swap Between CJ7 and YJ Question
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JohnEJo

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Southwest New Mexico
Vehicle(s)
1976 Jeep CJ7, 304, Quadra Trac
I currently have a ‘76 CJ7 with a 304 (dual exhaust) and an automatic. I’m looking to get a ‘94/‘95 YJ with a 4 cylinder and manual transmission. I like the YJ but wish it had a V8. What all would be involved if I were to swap the 304/auto out of the CJ7 and put it into the YJ? I know the transmission would have to be swapped since the AX5 can’t handle the V8 power and torque, but would it be would it be easier to keep the TH400 or find another manual transmission for it?

Thank you.
 
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JohnEJo said:
I currently have a ‘76 CJ7 with a 304 (dual exhaust) and an automatic. I’m looking to get a ‘94/‘95 YJ with a 4 cylinder and manual transmission. I like the YJ but wish it had a V8. What all would be involved if I were to swap the 304/auto out of the CJ7 and put it into the YJ? I know the transmission would have to be swapped since the AX5 can’t handle the V8 power and torque, but would it be would it be easier to keep the TH400 or find another manual transmission for it?

Thank you.
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The swap it self wouldn't be bad and you would have to keep the th400 as finding a transmission to fit an AMC and transfer case will be next to impossible. With that said next two problems are the rears. The Dana 35 in the YJ can't and won't hold up to the power of a V8 it's a terrible axle. As for the Dana 30 front the drop (where the drive shaft goes down) is the problem it's on the wrong side. In 87 when Chrysler took over they moved the drop from the passenger side where it's always been to the driver's side so now you're going to be able to use that axle.

If it's just the look your after it would be much easier to just put the YJ front clip on the CJ and be done with it

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Like Manic said, the front axle diff drop is on the wrong side, as far as the Dana 35, it will hold up fine with everyday driving, off road abuse is where the V8 will tear it up eventually.
To swap a V8 in a YJ, is not impossible, but basically a full on project, lose the ECM, and everything associated with it, a lot of rewiring, motor mount welding to frame, drive shaft lengths will be off, replace front diff with a CJ widetrack pass side diff drop, all doable, just expect to be without the Jeep for a while, and to keep standard, Novak makes adapters for all kinds of situations for add the AX15, or find a T4 4 speed direct bolt on, nothing money and time can't do. Unless you're getting rid of the CJ, just drive the YJ 4cyl. The conversion is just turning the YJ back into a CJ basically.
 
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You don't even need an ecm or wiring for the 304

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Also they make a bolt in V8 Cross member for the YJ I put one in years ago when I installed a 6.2 diesel into an 89 YJ TBH it might even be worth it to get a transfer case that will mate to the th400 with the drivers side drop if ur just looking for a cruiser

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Manic Mechanic said:
Also they make a bolt in V8 Cross member for the YJ I put one in years ago when I installed a 6.2 diesel into an 89 YJ TBH it might even be worth it to get a transfer case that will mate to the th400 with the drivers side drop if ur just looking for a cruiser

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That was probably the dumbest thing AMC did was to drop the V8 line with the introduction to the YJ
 
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That wasn't AMC Chrysler made the YJ and the V8 was dropped in 82 I think

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Thanks for the input everyone! Greatly appreciate it!

Correct me if I'm wrong, but I thought an AX15 from a 6 cylinder would bolt up to a 304 with no issues, and would also bolt up to the NP231? If that is the case, would that then take care of the drive-train part of this swap, except for the motor mounts which would have to be changed out? Would there also be any issues with the 304 since it has dual exhaust?

If I swap out the YJ AX5 for an AX15 to bolt up to the 304, would I have to change anything with the transmission mounts, cross members, or drive shafts?

And, someone said something about doing away with the ECM? So, would I just use the CJ engine wiring harness instead of the YJ's, and how easy or difficult would it be to hook up to the wiring harness at the firewall? And, would there be any issues with gauge calibrations between the two?

Oh, one more thing. What about the fuel system? If I remember correctly the YJ has a fuel injection system of some sort whereas the CJ7 is basic carburation, and if that is the case will I need to make any changes to the fuel system from the fuel tank to the motor?

BTW, the reason I am considering going with the YJ and swapping the 304 from the CJ7 to the YJ is that on the CJ7 I will have to do a complete rewire on it, plus it has significant rust issues whereas the YJ's only rust issue is the driver's floor pan. Not only that, but the YJ has a 4 cylinder and I tend to drive at highway speeds in the hills frequently.

Thanks again for all the input!!! It is very helpful!!!
 
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Oh, one more thing. In regards to the Dana 35, I have an extra Ford 9" housing with 28 spline axles with Torino bearings, no third member though, that I was contemplating swapping out the Dana 35 for. It was pulled from a 1974 Mercury Cougar with a factory 460 some time ago. While I understand that that Ford 9" is a beast and very stout, I also can tell from what I've read online it is not the favorite "go-to" rear end for Jeeps, but I have an extra one just sitting around doing nothing and thought I could make use of it in this build. The 9" has a width of 58.5", housing flange to housing flange. I have been unable to determine how that compares to the width of the YJ Dana 35 since I can't find housing flange to housing flange widths for those. If the size will work, would the 28 splines be sufficient, or will I need to go with 31 or 35 spline axles when I get the third member for it? The YJ currently has 31" tires on it, and while I may go to 33" tires at some point, I do not plan on going much higher than that. I am not looking to build a rock crawler or off-road beast of some sort, just something I can possibly use as a daily driver with occassional trips on moderate trails.
 
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You can make the 304 stand alone and leave the YJ harness be. Disconnect the YJ fuel pump as the 304 has a mechanical pump on the motor. You will need to use the 12v switch power from the YJ for the distributor. As for the ax15 the 4.0 I think is different from the 304 but can't confirm that

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Manic Mechanic said:
You can make the 304 stand alone and leave the YJ harness be. Disconnect the YJ fuel pump as the 304 has a mechanical pump on the motor. You will need to use the 12v switch power from the YJ for the distributor. As for the ax15 the 4.0 I think is different from the 304 but can't confirm that

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Okay. Thank you. That helps. I just did a quick check on the AX15, and Novak claims AX15's from 94-99 will work just fine, and AX15's from 88-93 will work if the 94-99 style retainer is used, so I would need to make sure what year I'm pulling it out of. :)
 
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Something to keep in mind the rewiring of the CJ would be easier to do than all the swapping around. Plus with a few simple modifications the YJ tub is a direct replacement for the CJ. I've done it to several Jeeps including mine

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Manic Mechanic said:
Something to keep in mind the rewiring of the CJ would be easier to do than all the swapping around. Plus with a few simple modifications the YJ tub is a direct replacement for the CJ. I've done it to several Jeeps including mine

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With the CJ7, it has both the Quadra Trac system and the narrow track axles, both of which I’m wanting to get away from. The YJ satisfies both of those objectives, so I find myself still leaning towards swapping the engines.

The AMC 304 is carbureted while the YJ has the fuel injected 2.5. Could the 304 utilize the fuel injection system, or at least part of it, and if so what would be needed for that? Would it be best to get a Holley Sniper setup for that, or would there be a better and more economical way to go? My understanding from reading other forum posts is that the 2.5 fuel pump within the fuel tank would be more than sufficient for it, or is that incorrect?

Oh, the 304 currently has a 2-bbl carb on it. If I were to go the Holley Sniper way, should I upgrade the intake manifold for a 4-bbl or would it be best to just stay with the 2-bbl intake?

Thank you.
 
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The sniper would be the way to go and no need to upgrade the intake as they make a direct replacement it's the sniper 2300. As far as the fuel pump no the one in the Jeep can't handle it. A lot of the early YJs both the 2.5 and 4.0 used an in tank pump but only ran about 40-45 psi fuel pressure. The sniper requires 60 psi which is what later Jeep fuel injection and other cars ran. Your best bet with the sniper is to get there in tank pump kit. I'm running inline pump with mine but only because I want easy replacement if needed on the trail. I plan on running the in tank pump and 2300 on my wife's 79 CJ 7 with the 304 and quadra Trac

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Manic Mechanic said:
The sniper would be the way to go and no need to upgrade the intake as they make a direct replacement it's the sniper 2300. As far as the fuel pump no the one in the Jeep can't handle it. A lot of the early YJs both the 2.5 and 4.0 used an in tank pump but only ran about 40-45 psi fuel pressure. The sniper requires 60 psi which is what later Jeep fuel injection and other cars ran. Your best bet with the sniper is to get there in tank pump kit. I'm running inline pump with mine but only because I want easy replacement if needed on the trail. I plan on running the in tank pump and 2300 on my wife's 79 CJ 7 with the 304 and quadra Trac

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Great! Thank you. It must be a pretty good way to go then since you’re doing the same thing. 😊
 
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Motor trend Engine Masters did an evaluation of the new Holley Sniper 2 a few days ago. Unfortunately right now the episode is only available on Apple TV or Motor Trend streaming.
tv.apple.com

Sniper 2 the Rescue - Engine Masters (Season 8, Episode 23) - Apple TV

Holley recently debuted the second iteration of its throttle body EFI system. We're here to see if it's any better than the first version and any bett…
tv.apple.com tv.apple.com


 
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