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V8 Conversion Questions

12K views 48 replies 13 participants last post by  devilrmk 
#1 ·
I've got a 95 YJ 2.5L 5 speed. This is a popular topic, but I had a few general questions to get me going. Everything runs fine right now but I'm going to start putting together ideas for a future V8 conversion. I've tried to read up a little to get familiar with it, but there's overwhelming amount of ideas and opinions. I'd like to start looking for donor vehicles. Couple questions I'd like opinions on to start narrowing my search.

  • What engine is easiest to put in and get going ? 350? LS?
  • I think I need to steer clear of highly electronic (newer) engines. Agree?
  • Do I need to get transmission that is already paired with engine?
  • Is it completely necessary to change axles with the added power?
  • Anybody know rough cost of having it installed?
I've got a friend I work with a lot on mechanical stuff, so I've considered doing the swap with him and paying for his time vs. having a shop do it, so I'd really like to have cost information from those with experience. This jeep is not my DD so I don't have to take that into consideration, cost will be main driver of decisions. Suggestions? Comments? Opinions? Thanks.
 
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#2 ·
I'm in that process right now... it's time consuming and far from cheap - and I'm doing the work myself!

1) I don't think any engine will make this "easy". You can find lots of info on doing it with an LS or a HEMI, just google and go nuts. AEV has lot of info for the HEMIs, and Novak has lots for the GM LS and some on Fords.
2) Not necessarily. It's simpler with a carb, but with FI all you need is the ECM and wiring harness. I went with a LY5 out of an 08 GMC Sierra (so trust me there's lot of electronics in there!) but when it's all done all that I will need is to plug in 5 wires and it will be good to go. You just need to simplify the harness and get rid of the useless stuff. Once again, AEV and Novak can help with that... or do it for you.
3) Once again: not necessarily. It might make things easier, but it might also yield you a very long powertrain if you take one out of a full size truck. Lots of companies make adapters so you can run almost any engine/tranny combination worth the trouble.
4) Axles should become the weakest link if the engine & tranny conversion is done right. It's not a bad idea to upgrade, but if you're short on coin your actual axles can last if you're very careful, but don't expect it to be a permanent setup.
5) Rule of the thumb is factor in about 5 grand for the engine swap, if you do most of it yourself. I'd say double that if you want to get someone else to do it. If any of your powertrain needs to be rebuilt, add that to the pile. Then add the price of axles (and most likely bigger tires) and you'll realize the extra fuel consumption won't be such a big concern after all... but the extra fun factor will make it more than worth it!
 
#3 ·
The axles (if you are easy while accelerating will hold up fine- just don't expect them to last if you are doing burn outs) I had the stock axles with my V8 conversion for years and no problems until pulling a boat at 5K lbs. I would go with a 5.3L out of a 2000-2003 GM. Cheap and lots of available parts. In '04, they went to an electronic throttle. I would put a 4L60 trans on it that came from a 4WD truck. That gets rid of having the trans torn apart for an NP231 main shaft. Then with the money saved on the engine and trans, I would splurge on an Atlas that mates to they trans and drops right. Tom Woods drive shaft and a radiator made for the conversion. Electronic 2200+ CFM pusher 16" fan. Pusher since it will fit in the grill and leave more space in the eng compartment. I would go with M.O.R.E. "bombproof" motor mounts, fool proof install. If you want more info, PM me and I'll fill you in on a lot more.
 
#4 ·
I did the 5.3L swap and LOVE it!!!! Getting over 20mpg and pass people going uphill! My stock axles held up fine but recently upgraded to D44's.

I have a COMPLETE write up on the swap on this forum, you should be able to find it.

Novak Engineering was a big help too. They have all the parts and knowledge to make the swap painless as possible.

Be ready to spend $4000+ to do it right. Worth every penny!
 
#5 ·
I am inprocess of doing a SBC conversion as well. A lot of information is available on these type of projects from Novak on their website. They have a lot of information on engines/transmissions/transfer cases, etc. that will help you decide.

I agree with others that have replied it is a big project but will all the resources available the biggest problems are time and money.
 
#8 ·
I'm in the same boat here myself and from what I have gathered, this is what I have found out:

What engine is easiest to put in and get going ? 350? LS?
Whichever engine you want to go with in the 300 size range. None are really easier than the other to get fitted in, you have to cut the motor mounts and weld in new ones regardless. Same goes for transmission crossmember.

I think I need to steer clear of highly electronic (newer) engines. Agree?
All in personal preference. OBD2 sure makes figuring out your problems a hell of a lot easier. It might seem like a lot more wiring to do, but it's really simple if you mark everything with tape when you remove the wiring and sensors.

Do I need to get transmission that is already paired with engine?
Up to you for what you want to use. For me, I am going with a manual setup. My donor engine is going to be a 5.2L out of a Grand Cherokee, which don't come in manual form. I am going with an AX15 or NV3550, whichever I come across first.

Is it completely necessary to change axles with the added power?
Absolutely. If you're going to go through the hassle of swapping in a bigger and more powerful engine, why would you not bother putting in a stronger set of axles?

The D30 front axle will be fine with a V8, even up to 35" tires, but the rear axle has got to go unless you plan on staying with 28" tires and driving like a grandma all of the time.

Anybody know rough cost of having it installed?
Depending on shop labor rates, you might be in it $1-2000 or you could be into it over $10,000. Not worth the time or effort.

Go find a donor vehicle that runs, passes smog (you want this to be legal, right?), has all the smog stuff in place, so on and so forth, and get to stripping it and your Jeep down. It seems like a lot of work, but it's really not. Welding in new motor mounts and modifying the crossmember is really all that has to be done to get the motor/trans/t-case in place. From there you just need to find a stronger rear end and adapt components, throw the harness in and do some splicing to your stock gauges, and you're nearly there. Some fuel supply modifying and small bits here and there.

I don't want to steal the thread but I was thinking about this in the future myself and was wondering about axles. I have heard a lot about the explorer axles. What do you think? Sorry for butting in.
The Ford Exploder 8.8 rear end is one of the most popular rear axles to swap into Jeep Wranglers. It's strong, readily available, and has a huge aftermarket support. Do some searching around the various forums for more info, there's likely more than a handful of threads about the swap.
 
#9 ·
What engine is easiest to put in and get going ? 350? LS?
No engine swap is easy but yes, GM based units have the most support and information out there with Dodge in a close second now.


I think I need to steer clear of highly electronic (newer) engines. Agree?
Newer engines make more power, use less gas doing it, and emit fewer emissions (in general) can be lighter and many are better built in stock form. Please take no offence if I am mistaken but it sounds like you are going to need a large amount of assistance anyway so why no go with a newer engine and gain all the benefits?

Do I need to get transmission that is already paired with engine?
Can be helpful and means less adaptors needed but it all depends on what you want out of your swap. Keep in mind changing transmission will mean a possible change in transfercase as well or perhaps major mods to make it work.


Is it completely necessary to change axles with the added power?
No not completely but encouraged. Your rear diff is particularly weak and almost any V8 swap will put major strain on it. However many have made the swap to V8 and kept their stock axles for some time. Know it's limitations and drive within them.


Anybody know rough cost of having it installed?
More than I would spend, but I can do it all myself. You can figure on taking your parts cost and adding at least that for labor. for that kind of cost, you had better think of keeping it forever.
 
#10 ·
great info dirttracker and xpress, I think my biggest blunder was starting my project with a jeep that had a 2.5L. It does fine off road for the most part but driving on roads and highways is where it lacks. If i would have started with a 6 cyl. I don't think I'd be considering a swap. I love my YJ though and I'm sure I'll figure it all out through time. I'd probably be willing to spend $5k, but any more than that probably isn't worth it. Thanks again guys.
 
#12 ·
I've got a local mechanic that is out of work I been discussing options with. He seems to think he could do the swap for $2k labor which sounds pretty good to me. So if I could get all the parts I might be in business. I'm gonna keep researching and possibly put this project in motion if I can find a deal on donor or crate.
 
#14 ·
If he wants to help, and you want to help him out, then by all means go for it. Welding skills are a must, no crappy welds.

As far as the 2.5L, it does great with the right tire and gearing combo. People don't give it enough credit, most think it's a weak pile of crap. It's actually pretty decently powered, and it's amazing that it can get a big heavy Jeep up to highway speeds without too much of a struggle for its size. I pulled mine out a few days ago and am still somewhat mind boggled at just how small it is, and I did 65-70 highways pretty easily on 29" tires...
 
#16 ·
I too have been planning a swap for myself. The cheapest my I figure to do it is buy a whole truck, chevy full size below 92(?) to have a 700r4 put motor trans and transfer all in. Swap from tbi to carb run aftermarket gauges ditch all the computer on the jeep. Should be able to find a decent running truck but a rough body for under 1500 sell unused parts off the truck and scrap the rest then sell my stock parts to get back some money. I plan on budgeting less than 4k and doing all work my self hope to have it together for more in the 3k area
 
#17 ·
Thats a lot of money and work to end up with a carbed setup. Carbs dont do well wheeling. Its honestly a whole lot less work and money to do it other ways and without chevy parts. You start throwing chevy stuff in the mix and you end up doing everything including axles.

Theres a lot to be said about keeping stock shifter locations, stock driveshafts, stock axles, stock gauges,etc. Saves a ton of time and money on the swap.
 
#18 ·
Thats a lot of money and work to end up with a carbed setup. Carbs dont do well wheeling. Its honestly a whole lot less work and money to do it other ways and without chevy parts. You start throwing chevy stuff in the mix and you end up doing everything including axles.

Theres a lot to be said about keeping stock shifter locations, stock driveshafts, stock axles, stock gauges,etc. Saves a ton of time and money on the swap.
For me, going v8 with a chevy trans 700r4 with matching transfer np241 seems like the best option. the 2.5 is junk in mine. seriously junk, trans, been rebuilt once already. PO had let it get in bad shape, body is perfect though. And i dont see it being any cheaper one bit to go different than chevy. the 350 has to be the most abundant motor made. Say a person did go 4.0, the motor it self i would think will cost more than a 350 then you'd still need a new trans the ax5 wont hold and around these parts a ax15 is quite hard to find. and transfer wont bolt up, different spline counts. With mine being 89 thats from the renix era so cant do the simple add two injector wires. would still need all the computer and wiring. If a person wanted to go v8 I see no better option for cheap reliable parts than chevy. And if you wanted Tbi get a 87 to 92 chevy that has tbi and the 700r so you dont have to deal with the electronics of the 4l60. To me half the fun is working on the jeep anyways.
 
#19 ·
My jeep is an 87, donor rig was a $500 wrecked grand cherokee that i profited from by the time i sold all other good parts. Ax15 and transfer case is from a dodge dakota that is simple to find at most junk yards. The 5.2 setup literally takes 4 wires to be spliced in to make the thing run. Everything looks factory, and feels factory.

A chevy setup requires even the axles to be swapped because of passenger drop t-case. Do your homework, im not kidding about the cost of my swap and the ease. I had it done in less than 3 weeks just nights and a weekend day or two. I swapped entire wiring harness, motor, trans and t-case. And if you wanted to go automatic it would be cheaper and easier, use grand cherokee setup complete.
 
#20 ·
I wasnt trying to offened you I was simply supporting my reasoning. And Fyi a chevy dosnt have passenger side drop. Its driver. the 241 is stouter that than the 231 and has just as much aftermarket support. sye and such. To each his own the 5.2 swaps are just as cool as the 350, the chevy way is just the way I myself plan on doing it.
 
#21 ·
No offense taken or intended. I was just trying to point out that there might be an easier cheaper way to do it. You guys are talking about spending more on a motor swap than i have into my entire jeep.
Newer chevy stuff must be drivers drop? I know older wasnt.
 
#22 ·
I have found a really good deal on a 1997 Grand Cherokee with the 5.2L and 46RH 4 speed auto. vehicle was rear ended and has frame damage, but engine is great and has $100k on it. I can probably get it for $1000 or less and then sell parts to come out even better. I just need to know what else I'll have to track down for the conversion. I don't think I want to use the auto, that would be a little strange for me in a jeep, so I'll probably look around for an AX15. Can I use the axles or anything else off the jeep cherokee? I would think sharing parts would be somewhat easier off a cherokee because it's a bit a sister to the wrangler. Thoughts?
 
#23 ·
Not sure on the rear axle but the front is low pinion. You dont want it, t-case will be a 249 probably, again you dont want it.

Parts needed. Drivers side exhaust manifold from a durango(jeep one wont clear starter), or block hugger headers, v6 dakota bellhousing, clutch hydraulics from a 95 wrangler, clutch and flywheel from a V8 ram, might have to source a different computer. Not sure about the obd2 stuff but the gc had security on the obd1. Pcm had to be from truck or van.
Pilot bearing adapter from dealer.

I know there is a couple more things but thats all i can think of at the moment.
Do some searching, i found all my info on the web from searching. Only thing i had to find out myself was the clutch slave. Dakota one is too big, doesnt give full engagement with wrangler master.
 
#26 ·
Well played Dirttracker! I'm definitely torn on what to do. I think I've narrowed the search down to 2 engines, the 5.2L or a chevy small block. Seems as though members of this site have done both and been happy with both. I thought buying that 97 cherokee with the 5.2L would make things easier having whole vehicle, especially with price being good. My mechanic told me to hold out for a SBC because they are easier to deal with. Pricewise it seems as though I can do the whole project for around $3,000 either way, so I'm cautiously moving forward trying to find me an engine or a donor now.:D
 
#27 ·
Find a donor. Reasons being are if it runs and drives right, you know that if you have an issue when you transplant it into your Jeep and it doesn't run right, you know it's something you did, which can help narrow things down.

Also they usually include all of the emissions stuff (it is a Federal crime to remove these components, and highly frowned upon here on this forum ;) ), wiring harness, computer, so on and so forth. That is why I am looking for a donor that runs, drives, and passes smog.
 
#29 ·
I posted this on Xpress's build thread as well, but looking for some answers. The cherokee I'm looking at has good engine and I can part out the rest of cherokee and end up breaking even or better, especially after selling my 2.5L. I'm just having trouble figuring out what all I can actually use off of it. I know I can buy motor mounts and get the 5.2L in just fine, but I don't know if the 46RH 4-speed will work, if the manifolds will work, or if the radiator will work? I'd like to be able to swap an AX-15 in to keep a manual, but not sure if that can bolt on, read a little bit about dodge dakota bell housing possibly working, but nothing for sure? I'm also not sure if the motor can be positioned so I don't have to get new driveshafts either? I'd like to go ahead and buy this cherokee because it's a hard to find deal, but don't want to find it's better to go another direction and end up having to try and sell. Obviously I've still got a ton of questions to wade through before I get too much farther. Anybody know or have experience on that?
 

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#30 ·
I just did my swap 2 months ago so its all fresh in memory. I used a 93 gc engine, bellhousing, ax15 and t-case from a dakota(if you already have an ax15 just get a bellhousing.
If you are switching to the ax15 you will need a different drivers side exhaust manifold. If staying with the auto it can all just be left as is.
I got all the info you need, will share this way or pm or whatever. Just do it. Dive in. Its really not that tough.

I stuffed my engine back about 2" farther than needed so i had to do driveshafts but i needed to anyway so thats why i chose to. You can place it in the correct spot for your driveshafts no problem. I have about 10" between radiator and water pump(electric fan)

Radiator will need to be changed, neither will work. I used an aluminum one from summit racing that cost me $140. Just had to fab brackets.
 
#34 ·
That's pretty much what I expected and even hoped to hear. I would like to do the engine swap, keep my stock driveshafts and axles until I'm ready for stage 2 (8.8 and maybe sye), that way it's not a huge hit financially all at once. It's got the AX5 right now, which definitely won't work, so I'll either keep the auto that's on the donor or bolt on an AX15. I don't have a lot of mechanical knowledge, just enough to get me in over my head, but I've got a good mechanic who helps me a lot. I'm getting close to diving in, but dread the thought of my jeep sitting in garage for months on end while I deal with all the unexpected and pour more $ into it than anticipated. Seems as though everybody who has done a swap says it was PITA but well worth it after all said and done.
Parts list I've put together so far:

  • 5.2L from donor $0 to $500 depending on difference
  • Motor mounts $230.00
  • Headers $300 - most likely needed
  • Radiator $200
  • AX15 Tranny $200 - optional
  • Misc Parts $800 - junk yard and unexpected
  • Labor help $2000 - generous
So essentially I'm planning a $4k project swap and definitely don't want to spend more than that (whole jeep cost me $4500).

(and yes mudd it is frame damaged, which is why i can get it on the cheap)
 
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