WJ 4.7L V8 swap into XJ?

I've had this thought in the back of my mind since I put the stroker into my XJ 19k miles ago. Does anybody know of this swap being done? I've found this link of the 4.7L being put into a TJ. http://www.burnsvilleoffroad.com/articles/00_12.aspx

I like the engine because the power is respectable in base form, more power is on tap with mods, and performance should be strong in a 3400 lb XJ. Fuel mileage is better than the 318 or 360, and both of those engines are heavier. The engine and auto tranny package is 2" shorter than the 4.0 package. Wiring shouldn't be too bad since I'm staying with Chryser products. Any thoughts on the swap? Now I just need to find a totaled WJ with a good drivetrain.

Why not a 5.7L Hemi? It's a chrysler too and would deff be interesting.

A stock 4.7 puts out less HP/TQ than a 4.6 stroker so there's no rational reason for that swap unless you add quite a few mods to the 4.7.
If you're going to do a V8 swap at all into an XJ, I'd suggest a Chevy 5.7 LS1. It's all aluminium (100lb lighter than a 4.0), compact, cheaper to buy than a Chrysler 4.7, puts out ~100hp more than a 4.7, huge aftermarket for mods, and Novak Conversions have the bellhousing adapter for the swap.

Dr. Dyno said:

A stock 4.7 puts out less HP/TQ than a 4.6 stroker so there's no rational reason for that swap unless you add quite a few mods to the 4.7.
If you're going to do a V8 swap at all into an XJ, I'd suggest a Chevy 5.7 LS1. It's all aluminium (100lb lighter than a 4.0), compact, cheaper to buy than a Chrysler 4.7, puts out ~100hp more than a 4.7, huge aftermarket for mods, and Novak Conversions have the bellhousing adapter for the swap.

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A stock 4.7 puts out 235, 265 if the H.O. A stock 4.6 puts out maybe 220hp without mods. Put those same mods on the 4.7 as you did on the 4.6 to get your claimed 260hp and that 4.7 will be around 300hp....
From your very own sticky on JU dino
http://www.jeepsunlimited.com/forums/showthread.php?t=626553

4.7 V8 (Factory ratings 235hp@4800rpm/295lbft@3200rpm)

Stage 1 (285hp@4700rpm/380lbft@3800rpm)

K&N FIPK
Brian Stroud's RamIT cold air intake
Kolak 3" cat-back exhaust
Modified Y-pipe + 3" high-flow cat
Mopar Performance PCM flash, Kenne-Bell Optimizer II, or Superchips Microtuner
F&B 70mm TB
KRC Performance HO camshafts & intake manifold
Remove clutch fan + short belt PS/alternator bypass
Duner's custom fuel rail cooling system



Id still run an LS1 if I could though.

I'm not a big fan of the 5.7Hemi, so I'll stay clear of that option. I'd love to run an LS1, but I think I could find a totaled WJ for cheaper than the Chevy drivetrain. I also want to swap in the 5 speed auto trans from a WJ.

Also Dino, I definitely wouldn't keep the 4.7 stock? I'd have to fabricate some custom exhaust, so I'd definitely go with a 3" y-pipe and catback.

This swap is still in the brainstorming stage. My stroker took almost 2 year to collect parts and install the engine. Look for a finished swap by 2010.

the new 4.7 puts out 300hp

BIgDaddyChia said:

the new 4.7 puts out 300hp

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http://www.allpar.com/mopar/47.html

I think they're calling it the semi-hemi. Not gonna find one of these in the junkyards for cheap though.

Considering that the SBChevvy swap is fairly common, and I've heard of a BBChevvy swap going in, I don't see any reason why it can't be done! Hell, anything can be done if you're willing to work at it.

However, it would seem that you'd get more top-end power at the expense of bottom-end torque, and isn't bottom-end torque why we just love the XJ? I could be wrong - but the problem with the Hemi V8-345 is that there aren't that many mods out there, while the SBChevvy and BBChevvy have been around for a good forty years or so, and you can build each of them entirely from aftermarket parts, if you so choose.

Now, swap in a Cummins six, and we're on to something! But, don't let me discourage you! Just don't expect it to be an easy swap, and please do document it if you decide to do it (I'd love to hear about it, but I've got a strange idea to want to swap in a V8-426 Hemi into an XJ body anyhow. I'm strange, I'll admit...)

5-90 said:

However, it would seem that you'd get more top-end power at the expense of bottom-end torque, and isn't bottom-end torque why we just love the XJ?

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I see a lot of this type of stuff on this site. If a 4.0 is making more torque than a V-8 then a couple plug wires were left off the 8. Let's look at your typical small block chevy. 350 ci, probably smog inhibited. Now if someone were to take the time to swap it in, assume it'd be running right first. Stuff that'd be done during a typical rebuild- rv cam at the least, maybe a Performer intake, 4 barrel carb or hopefully EFI, since it's going in a Jeep. No smog parts, but not a race motor either- just a cheap, mild performance overhaul. This hypothetical sbc is going to make at least 300, more like 350 lb/ ft of torque, at a low rpm.

So explain how the almighty 4.0 out-torques it or any other larger displacement engine?

JJacobs said:

I see a lot of this type of stuff on this site. If a 4.0 is making more torque than a V-8 then a couple plug wires were left off the 8. Let's look at your typical small block chevy. 350 ci, probably smog inhibited. Now if someone were to take the time to swap it in, assume it'd be running right first. Stuff that'd be done during a typical rebuild- rv cam at the least, maybe a Performer intake, 4 barrel carb or hopefully EFI, since it's going in a Jeep. No smog parts, but not a race motor either- just a cheap, mild performance overhaul. This hypothetical sbc is going to make at least 300, more like 350 lb/ ft of torque, at a low rpm.

So explain how the almighty 4.0 out-torques it or any other larger displacement engine?

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You may have misread what I was trying to say. It's certainly possible that a V8 will outpower a six (V6 or I6) - but what I'm referring to is the crankshaft speeds at which that power is made.

A hallmark of the inline six is relatively high torque production (85-90% of peak or better) from off-idle at about 1000rpm to somewhere around 3500-3800rpm or so, with a slight falling-off to 5252rpm when horsepower output takes over. You get loads of low-end torque at low crankshaft speeds, and a nice, flat torque curve until around 4500-5000rpm or so, when it finally starts to fall off rather sharply (usually.)

A V8 usually has more pronounced "peaks" in the torque output and power output curves, with a torque "peak" typically at a higher crankshaft speed. Since "best cruise" tends to be right around peak torque output, you will typically note different axle gearing for the I6 and V8, assuming the same transmission ratios. (Of course, if the transmission ratios have been changed, all bets are off.)

I'm not going to say with certainty that one type of engine is better than the other. It all depends on how it's used. For what I do, for instance, I find an inline six to be better suited to my needs. I get roughly V8 torque at a lower RPM, with less displacement (and therefore lower fuel consumption!) and easier access to various parts - a V8, after all, is about three times as wide as an inline six.

Does this make the V8 useless? Not for you - if that's what you need or want. You'll just have to "wind it up" a little more if you want grunt - but I've seen (and built) some stump-pulling V8 engines. I just don't like to run engines very fast, and I'd rather cruise down around 2500rpm than up around 4000rpm or so.

Anyone who tells you that one type of engine is "better" than the other has left off two critical words - "for me." I think an inline six is better for me - and most of the people here are of a similar mind. A six isn't better for everyone, nor will it be, as we all use our rigs differently. Quoth Slowhand, "It's in the way that you use it."

Have you measure the width of a 4.7 yet? They are wide I really wanted to put the 4.7 in to but I don't an xj got the room for width without some mods. Now a 318 fits pretty good.

5-90 said:

....Now, swap in a Cummins six, and we're on to something!...

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thats what I'm talkin about :guitar:
even the cumimins 4.0 4 banger would be bitchin:greensmok

5-90- I guess that's where we're going to have to disagree. I would say if you had a 350 underhood, 302, whatever.. versus a 4.0 or even 4.6, at a given low rpm while cruising say 2500. 1/3 throttle on the V-8 is going to get a lot more results than 1/3 throttle on the I-6. That's because the larger displacement of the v-8 makes more low rpm torque than the 6. I don't know why you say a mild v-8 is peaky, in my opinion they're anything but- and you have to wind the i-6 up to get it to do anything. Maybe engines work backwards in CA?

jeepinwi said:

I'd love to run an LS1, but I think I could find a totaled WJ for cheaper than the Chevy drivetrain.

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I can get a complete used low-mileage turnkey LS1 engine with all accessories, wiring harness, and engine computer over here for little over $2500. I'm sure you could find one for a comparable price. The only reason I haven't done it in my Jeep is that it would fail the annual vehicle inspection because of the non-standard engine.

jeepinwi said:

Also Dino, I definitely wouldn't keep the 4.7 stock? I'd have to fabricate some custom exhaust, so I'd definitely go with a 3" y-pipe and catback.

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No doubt, but you'll still only have about 285hp even with a bunch of bolt-on mods and you'll need KRC Performance heads to breach 300hp. Is it really worth all that trouble to get a mere 40hp more than a 4.6 stroker? You can get an easy 400hp out of an LS1 with the same bolt-ons and it'll be far more rewarding.

JJacobs said:

you have to wind the i-6 up to get it to do anything.

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I'm not going to enter the I6 vs V8 debate. Aside from that, I completely disagree. I am constantly impressed with what this motor is capable of at rpms just over idle. What do you consider 'anything'? It does have a lot of passing/accelerating power at and around 4k, but any other vehicle I've driven (particularly my Dad's KJ) doesn't start making power until then.

It's just that if you're considering a swap and decide to stick with a stroker, you're missing out unless you boost it. Yeah, they make good power and don't take any fab work to install. But, a V-8 will handily out-torque it. 8 cylinder engines are widely known for low-end torque. I'm kind of at a loss how this forum has it spun around that V-8's are peaky, high rpm motors. Any time I've had to make an inline get some work done on the passes around here, it took a lot of rpm to make it happen at the speed I wanted.

5.2poweredxj, do you really have to wind that thing up to get it moving?

JJacobs said:

But, a V-8 will handily out-torque it. 8 cylinder engines are widely known for low-end torque. I'm kind of at a loss how this forum has it spun around that V-8's are peaky, high rpm motors. Any time I've had to make an inline get some work done on the passes around here, it took a lot of rpm to make it happen at the speed I wanted.

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Actually, it's the I6 that's known for its strong low rev torque, not the V8. Ever wondered why some of the torquiest diesels on the planet are I6's (Cummins 5.9 is a good example)? V8's of the same displacement have a shorter stroke and more valve area, so they breathe better at higher revs but the shorter stroke means less low rev torque.
If you compare a 4.7 I6 stroker to a 4.7 HO V8, the stroker makes more torque at lower revs and it's only above ~4000rpm that the V8 begins to turn the tables. The bottom line is that if you want low rev grunt, a big displacement I6 is the way to go. Yes, a V8 can also make big torque at low revs but it'll require a longer stroke and smaller bore to do it.

Dr. Dyno said:

The bottom line is that if you want low rev grunt, a big displacement I6 is the way to go. Yes, a V8 can also make big torque at low revs but it'll require a longer stroke and smaller bore to do it.

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The history of the V8 doesn't just revolve around short stroke high rpm engine architecture. I grew up in an 'Olds' family, 4.125 bore/4.250 stroke, it was all about torque.
Around here, rpm gets my Jeep up the mountains. 225 ft/lb doesn't cut it. A stroker would give me plenty more torque at an rpm my Jeep just doesn't spend much time at.

Dr. Dyno said:

Actually, it's the I6 that's known for its strong low rev torque, not the V8. Ever wondered why some of the torquiest diesels on the planet are I6's (Cummins 5.9 is a good example)? V8's of the same displacement have a shorter stroke and more valve area, so they breathe better at higher revs but the shorter stroke means less low rev torque.
If you compare a 4.7 I6 stroker to a 4.7 HO V8, the stroker makes more torque at lower revs and it's only above ~4000rpm that the V8 begins to turn the tables. The bottom line is that if you want low rev grunt, a big displacement I6 is the way to go. Yes, a V8 can also make big torque at low revs but it'll require a longer stroke and smaller bore to do it.

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The 4.7 HO won't even fit in an xj. If you talk about a motor that will- a 2-valve, pushrod one- the torque story is different.

All this talk of V8 vs I6 is a bunch of bull sh!t without looking at the dyno charts. Peak numbers on a spec sheet mean nothing, it's the shape of the curve that makes the difference.

On a budget, rebuild what you have. If you are worried about the unknowns keep a stock displacement and get on with life.

I like the idea of a smallish displacement V8. Meets the original engine's performance numbers without dropping a big engine in the engine bay that will burn more fuel. Personally, I don't need more power out of my Jeep's engine. What i'd like is modern, clean burning and better MPG with the same performance I have now. I wouldn't be surprised if a modern V8 (LSx, Chryco, 1UZ) of similar displacement to the AMC 4.0 with modern EFI systems would get better MPG numbers.

The way I see it there are three completely viable V8 swaps out there:

1.) Chev LSx/Vortec, 4L60E and PCM adapted to the Jeep t-case
2.) ChryCo V8, trans, t-case and PCM adapted to the chassis
3.) Toyota 1UZ and PCM adapted to the Jeep AW4 and t-case.

Or some variation of the above depending on your needs/desires.

You could do old school Chev Gen I SBC but for the amount of work required why bother when you can do the new stuff? I have an old EFI SBC lying around and I still wouldn't go that route. The new stuff is just so much nicer.

I'm a fan of the AMC V8 swap just for the coolness factor... but wouldn't do it myself for various reasons.

Ultimately, which one you do depends on which church of power you pray to.

Trying to swing back on topic...

I've seen the 4.7 swap discussed here many times but to my knowledge it has never been done. If you feel confident it can be done and have reasonable welding, wrenching, wiring skills I say go for it. It'll be semi-original and with the right attitude and attention to detail it can be made to work quite nicely.