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Lexus 4.0 engine swap ??

1

1badxlxj

NAXJA Forum User
Location
i'm over here
Just wandering if anyone has ever heard of or attempted a engine swap in there cherokee using a lexus engine?

The engine is a direct bolt in to the AW-4 tranny using the lexus bellhousing, just need to fab engine mounts and wire it in.

The lexus 4.0 V-8 weighs less and makes twice the power & torque over the jeep 258.
 
Interesting...

1) You're comparing the Lexus V8 to the AMC258, which has been out of production for 15 years or so, didn't have modern controls, and was a good engine, but could have been better.

2) You're comparing "peak" numbers - which can be "apples to oranges." If you want to really compare engine performance for a given application, figure out what that engine is going to be used for. Don't look at peak numbers for both engines, take a look at the performance of both engines from off-idle to about 3000rpm. Most V8 engines end up making their peak torque at around 4000-4500rpm, with a rather "sharp" or "pronounced" torque peak. An advantage of the inline six is that the torque "peak" isn't really - it's more of a torque "plateau," and the actual "peak" itself happens at a much lower rpm than a V6 or V8 engine. The AMC242, for instance, makes around 80% or so of peak torque "off-idle," which is where it needs to be in a truck engine. Most V8s are somewhere under 50% - usually far under.

I'm not trying to run down the idea - just give some airtime to the thinking that should go into it, and perhaps to help figure out why it hasn't been done yet... Few things give all the details that should be borne in mind at first gloss, y'know...

5-90
 
uh isnt the bellhousind casted to the trans on the aw4? good luck tyin to seperate them then
 
These are all things i am taking in to consideration. That is why i have posted this idea here to get feed back. The lexus/toyota 1UZ-FE engine spec's are 250hp @ 5600rpm & 260 ft/tq @ 4400 rpms.

The 4.0 jeep engine spec's are 177hp @ 4200rpm & 190ft/tq @ 4000rpm

Both of these engine spec's are for the 1990 year models.

I so far can't find a hp and tq graph for these two engines. But also taking into consideration the vehicle it will be going into and its 5-13 gear ratio and 4-1 low range t-case turning 44 inch TSL's. I have wheeled it for years with the stock 4.0 and am now wanting more power. as it is on most hill climbs I am hitting the 4000 rpm range anyway. And in 2-wheel drive forget about power. Max speed is about 40 mph and it struggles to get there.

The whole reason this came about is that a freind just happens to have a wrecked 90 lexus ls400 that still runs great. and i can get it for no money. He just wants some jeep parts that i'm not going to use anyway.
 
5-90 said:
Interesting...

1) You're comparing the Lexus V8 to the AMC258, which has been out of production for 15 years or so, didn't have modern controls, and was a good engine, but could have been better.

2) You're comparing "peak" numbers - which can be "apples to oranges." If you want to really compare engine performance for a given application, figure out what that engine is going to be used for. Don't look at peak numbers for both engines, take a look at the performance of both engines from off-idle to about 3000rpm. Most V8 engines end up making their peak torque at around 4000-4500rpm, with a rather "sharp" or "pronounced" torque peak. An advantage of the inline six is that the torque "peak" isn't really - it's more of a torque "plateau," and the actual "peak" itself happens at a much lower rpm than a V6 or V8 engine. The AMC242, for instance, makes around 80% or so of peak torque "off-idle," which is where it needs to be in a truck engine. Most V8s are somewhere under 50% - usually far under.

I'm not trying to run down the idea - just give some airtime to the thinking that should go into it, and perhaps to help figure out why it hasn't been done yet... Few things give all the details that should be borne in mind at first gloss, y'know...

5-90
Click to expand...

Leave it to you to beat me to the punch......
 
The aw4 tranny has a removable bellhousing like any manuel tranny. It was used in 4runners, jeep xj, and lexus

Yes i meant to say 242 4.0l not 258, My bad
 
1badxlxj said:
These are all things i am taking in to consideration. That is why i have posted this idea here to get feed back. The lexus/toyota 1UZ-FE engine spec's are 250hp @ 5600rpm & 260 ft/tq @ 4400 rpms.

The 4.0 jeep engine spec's are 177hp @ 4200rpm & 190ft/tq @ 4000rpm

Both of these engine spec's are for the 1990 year models.

I so far can't find a hp and tq graph for these two engines. But also taking into consideration the vehicle it will be going into and its 5-13 gear ratio and 4-1 low range t-case turning 44 inch TSL's. I have wheeled it for years with the stock 4.0 and am now wanting more power. as it is on most hill climbs I am hitting the 4000 rpm range anyway. And in 2-wheel drive forget about power. Max speed is about 40 mph and it struggles to get there.

The whole reason this came about is that a freind just happens to have a wrecked 90 lexus ls400 that still runs great. and i can get it for no money. He just wants some jeep parts that i'm not going to use anyway.
Click to expand...


Those are still "peak" numbers - check the graphs. I'll have to see if I have some .jpgs of sim graphs lying about - I backchecked Desktop Dyno some years ago, and while its numbers are "optomistic," its curves are spot-on (just a little higher than they should be - but from what I've found, Desktop Dyno doesn't account for parasitic drag.)

Gimme the specs on the Lexus plant, and I can run the two side-by-side.

5-90
 
ROBZ95Xj said:
uh isnt the bellhousind casted to the trans on the aw4? good luck tyin to seperate them then
Click to expand...
It's removable - notice it's missing in this pic:
aw4.jpg


That comes in handy when your bellhousing looks like this:
aw4_2.jpg
 
Is there any savings of money and time for installing something foreign into the engine compartment (ecu,harness,custom exhaust/intake,etc.) versus the power gained by stroking your 4.0?

I'd think in the long run you'd be ahead spending the money to stroke your 6 rather than the time you would spend installing a lexus 8.
 
Like what 5-90 said, check the curves before committing.

That said, the Lexus cars are incredibly "drivable" which implies a relative high/flat torque curve near the bottom end of the RPM range. That's an implication, not reality without verification.

Was that vintage Lexus SOHC or DOHC? This will tell us a little about the shape of the curve too. That said, if it has variable cam geometry all bets are off.

IMO, for a DD style XJ, the Lexus 4.0 would be a very good choice given no adapters would be required.
 
I love my XJ to death, but if you want a V8 Jeep, buy one! They are everywhere and are relatively cheap.

The Chrysler V8s in the ZJ and WJ have quite a good torque curve as far as I know and will be far more docile than a peaky 4.0 Lexus V8.

But as always, if it was me, I'd just build a 4.7 stroker and be done with it.
 
This is what, the 1UZ-FE? I always liked the 3UZ-FE myself

4.3 L (4292 cc) version. Bore is 91 mm and stroke is 82.5 mm. Output is 290 to 300 hp at 5600 rpm with 325 ft·lbs of torque at 3400 rpm. It has an aluminum engine block and aluminum DOHC cylinder heads. It uses SEFI fuel injection, has 4 valves per cylinder with VVT-i.

21_3.jpg
 
Last edited:
don't listen to them! i'm gonna stroke mine, because i don't feel like messing with a swap. if you have a free engine though...an aluminum v8 would be pretty sweet methinks :). if it'll fit, do it! and as far as the engine being peaky...pffft...when you are talkin' about an extra 60 lb-ft at peak, you aren't gonna miss anything at off-roading rpms. i'm sure the numbers at least match the jeep at low revs. besides...i don't know what everyone is smoking around here...the 4.0 I6 is not really that torquey at the low end! i dunno if that is sacrilege to say that or what...but i said it! i have to down shift all day long to climb grades. this is one of the only vehicles i have owned (non 4-cyl) that needed that.
 
PapaPump said:
besides...i don't know what everyone is smoking around here...the 4.0 I6 is not really that torquey at the low end!
Click to expand...

:bs:

Go drive a Ford SOHC 4.0 V6 or any modern V6 for that matter. My bud has a Ford Ranger with that engine and its a slug until it "hits the cam" at about 3000-3500 rpm. And thats at wide open throttle. The part throttle response is worse. And his Ford Ranger even has 4.10 gears.

The Jeep 4.0 "hits the cam" so soon, and so quickly that its not noticable. There isn't a torque peak that you can feel, it simply makes good torque at all rpms.
 
my last truck was a ranger with the older v-6...155 horse, 220lb-ft. it had a much better feeling of low-down torque...same gearing (3.08/3.07), nearly the same size tires...jeep came with 205/75r15s and the ranger had 225/75r14s. admittedly, the jeep has bigger tires (still just 235/75r15s), but the ranger was heavier.

newer ford OHC motors seems to have lost the feeling of low-end torque, but i still think my brother's ranger has more pull (same as your buds). haven't tried the bumper pull!

anyway, sorry for pulling the thread off topic! put in the v8!!! i wanna see it.
 
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