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Jeep 4.0 Straight 6


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Been toying around with this idea in my head for a while now. I haven't measured it yet, but it seems like the two engines (L28 and Jeep 4.0) have similar external dimensions. I'm sure the Jeep mill is bigger, but not by too much. The latest Cherokee engines are rated for 190 horsepower and 225 Lb. Ft. of torque. Not exactly a powerhouse, but more than enough to get a 2500 lb car moving along pretty quickly. Adapting a T-56 to one would make good use of all that torque. Gas mileage probably wouldn't be too shabby either. The Jeep engine is also IMO one of the most reliable engines ever built, anywhere. Performance parts are available. A 300+ HP NA built would be pretty reasonable. I have other plans for both of my Z's, but if I someday manage to pick up a third Z car, it might just end up with one of these. Thoughts, opinions?

 

Mike

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Sounds cool, but in my experiance (limited as it is) jeep is not known for great gas mileage. Of course jeeps are similar in shape to a certain masonary product which is used extensively in the construction of comercial buildings in the midwest.

 

When I drove them, the 4.0L Grand Cherokee was a bog dog and the 5.3L wanted to jump when you touched the pedal. Although with the right gearing, the 4.0 was said to be a stump puller.

 

I also heard that parts for the jeep are hard to get with limited aftermarket support, just check that out before the decision is made.

 

But you know there was one other engine choice that fits perfectly in a Z and mates to the t56... What the heck was that... hmmm... great power, gobs of torque, stout too... superb efficiency... ah it'll come to me.?!

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I've also thought it through, there is actually plenty of aftermarket support for these motors. They have a pretty significant stroker kit for them. On the other hand they are pretty low-tech, being a pushrod motor and all. If i was gonna consider a inline 6 truck motor with that big displacement, it would def. be the newer trailblazer motors. 4.0 liters (i think) DOHC. . . and from what I hear a supra 6 speed can be mated to them. there was a recent issue of hot rod mag which had a chevy nomad with one of these bad boys in it. Turbocharged, custom manifolds, 800hp+ easy. Its like a supra motor with an extra liter!!

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Sounds cool' date=' but in my experiance (limited as it is) jeep is not known for great gas mileage. Of course jeeps are similar in shape to a certain masonary product which is used extensively in the construction of comercial buildings in the midwest.

 

When I drove them, the 4.0L Grand Cherokee was a bog dog and the 5.3L wanted to jump when you touched the pedal. Although with the right gearing, the 4.0 was said to be a stump puller.

 

I also heard that parts for the jeep are hard to get with limited aftermarket support, just check that out before the decision is made.

 

But you know there was one other engine choice that fits perfectly in a Z and mates to the t56... What the heck was that... hmmm... great power, gobs of torque, stout too... superb efficiency... ah it'll come to me.?![/quote']

 

The gas mileage is an issue with these. Mine gets 15 to 16 MPG, no matter what I'm doing with it. Could be highway cruising, pulling stumps, AutoX (pretend for a minute that it is not a 3700 lb 4X4). 15 Mpg. I have a feeling that would change with the 1000 pound weight reduction and the .5 sixth gear. Granted, this would not be as much as a performer as the LS1, or just about any other engine swap, but it would be dead reliable, and would have a unique cool factor to it. The weight would be an issue too, although I'm not certain of the exact all up weight of these. Probably pretty close to an iron head SBC.

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If you are planning on using your jeep as the doner than it's free? Can't beat that! A new LS1 T56 is $2000 minus the bellhousing, but used or rebuilt they could go for much less. I would be surprised of that 15 didn't go to 18-22 avg in a Z with a 3.54 rear and .5 6th.

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If you are planning on using your jeep as the doner than it's free? Can't beat that! A new LS1 T56 is $2000 minus the bellhousing, but used or rebuilt they could go for much less. I would be surprised of that 15 didn't go to 18-22 avg in a Z with a 3.54 rear and .5 6th.

 

Nah, I like my jeep too much to tear it apart for parts. They have a few in the junkyards out here though. Oddly enough, just about every one I've seen has been wrecked. It seems the only way to kill them is impact trauma. I normally suspect engine problems on cars that make it to the junkyard intact, very few jeeps end up there unless they are crumpled up pretty good. I already have a T56, but it's getting bolted up to a 383 for my 240Z. Right now I'm just toying around with ideas for a possible engine swap for my 280Z. It's L28 is pretty sick, wont run well enough to pass smog for registration. I'm going to try a few more ideas for fixing it, if that fails it's getting yanked and replaced with something faster/stronger/better. Another idea I had was to use a 7MGE out of either a Cressida or NA Supra. They look like they would fit pretty easily....

 

Mike

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1978... what a shame the rolling smog law was stopped. You'd be smog free by now. Did you ever research the paperwork necessary from the DMV to replace the engine with a newer one out of a different car? I know it's legal but I think it involves a referee check, a fee and some paperwork.

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I'm actually tryingto get it registered in AZ. Surprisingly, Arizona has worse smog laws than the Peoples Republic of Kalifornia does. In the Tucson or Phoenix metro areas, the car has to be smog tested if it is 1967 or newer. 1967!!!!! Did they even know what hydrocarbons or carbon monoxide were in 1967? :) At any rate, I have some more research to do concerning engine swaps and smog laws before I try anything with the 280Z. Hopefully I can figure out why the engine runs so badly and fix it before having to resort to engine replacement. The problem seems to be with the injection and engine management system rather than a mechanical problem with the engine.

 

Mike

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I had a 1997 Grand Cherokee and I loved it's I-6, but it doesn't belong in a sports car.

 

If you want to seriously consider a truck motor, the Chevy Trailblazer's Vortec 4200 I-6 might be a better choice

 

The Vortec 4200 is a 4.2-liter, inline six-cylinder, all-aluminum, dual-overhead-cam, four-valves-per-cylinder design engine. the engine delivers 275 hp and 275 lb-ft of torque.

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  • 2 weeks later...

Hmmm, that sounds interesting. They currently have a few of those on ebay now for cheap too. 10.3-1 compression ratio is pretty stout for a stock engine, must have a pretty good cylinder head design to pull that off on 87 octane. Depending on the outcome of my engine troubles with the 280Z, I might seriously look into the 4.2. Thanks for the tip!

 

Mike

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I've had my jeep since 93 and hand no problems except the CAS sensor failing (that is what plague these engines, and would suggest to replace it anyways if you do attemp this endevore). Its a 145k miles and thats the only problem I incountered.

 

All the power on these engines is pretty much below 4k rpms so I suggest in getting one from 1996+ so you can flash the ecu with new maps (OBD II).

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Not to try and steel this thread, but what about going the other direction?? What do you guys think of a L24 in a 1957 Jeep. My grandpa just passed away so I inherited some cars (as well as a 1964 Monza Spyder Turbo :-). The jeep is going to need alot of custom fab work done anyways from 30 years of sitting in a field. So thats not going to turn me away. I am going to rip the L24 out of my 240 so I will have an extra motor just sitting around.

 

I guess my main question is would the L24 be worth putting in there? Is it a motor that could handle the off road punishment and such without falling apart? The Jeep has a straight 6 in it right now so I assume it would fit but I need to measure it. Any ideas on how to get the engine to work with the 4 wheel drive system??

 

I know this should probably be on a jeep forum, but I figured I would try here first. Thanks for any ideas guys!

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L24 doesn't have enough power to move a car that weighs almost twice a 240z. To get to make that much power isn't worth it if for a jeep IMO. the AMC based L6 produces alot more torque than the L24. All that custom fab work to have a jeep L6 in a z car is almost the same amount of work to put any other engine into these cars IMO.

 

To get a L24 to work with the jeep's 4WD you would need to have the jeep tranny fit on the L24 and would most likely need a custom bell housing.

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L24 doesn't have enough power to move a car that weighs almost twice a 240z. To get to make that much power isn't worth it if for a jeep IMO. the AMC based L6 produces alot more torque than the L24. All that custom fab work to have a jeep L6 in a z car is almost the same amount of work to put any other engine into these cars IMO.

 

To get a L24 to work with the jeep's 4WD you would need to have the jeep tranny fit on the L24 and would most likely need a custom bell housing.

 

Well' date=' I guess it sounded like a better idea in my head. For some reason I wasnt thinking of the added weight...but it is a 1957. I know for a fact that it weighs no where near what today's jeeps do. This thing is tiny. I know the motor that is in it right now is a Ford straight 6, not sure of the displacement. It's an [b']OLD[/b] one that's completely stock with a single 2bbl carb on it. Am I wrong in assuming that a L24 would be putting out as much as if not more power???

 

Also, total power output doesn't concern me too much. There are many things that can be done with gearing to make a motor putting out 150 whp pull a tree out of the ground. I am not too concerned with gas milage, top speed or cruising rpm's as this would see only dirt roads and hill climbs by my house.

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Well' date=' I guess it sounded like a better idea in my head. For some reason I wasnt thinking of the added weight...but it is a 1957. I know for a fact that it weighs no where near what today's jeeps do. This thing is tiny. I know the motor that is in it right now is a Ford straight 6, not sure of the displacement. It's an [b']OLD[/b] one that's completely stock with a single 2bbl carb on it. Am I wrong in assuming that a L24 would be putting out as much as if not more power???

 

Also, total power output doesn't concern me too much. There are many things that can be done with gearing to make a motor putting out 150 whp pull a tree out of the ground. I am not too concerned with gas milage, top speed or cruising rpm's as this would see only dirt roads and hill climbs by my house.

Your jeep has a ford engine? I thought that jeep was owned by AMC and then sold to Dodge/Chrysler. Or something weird happend and you happen to have a ford in your jeep.

 

Gearing can only take you so far. The nissan engines, even though they are L6s, don't really produce all that much torque. With the example of stump pulling, HP doesn't really matter much its the torque that is what does most of the pulling power.

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For some reason I thought that the L series motors were fairly torquey, I could be wrong though, maybe thats just the L28. And yes, the origional motor was pulled out, from what I understand, about 20 years ago and a Ford straight 6 and steering assembly was put in.

 

So you don't think that with some 5.xx gears that it would be enough to get it moving well? It's not that I MUST use the Z motor in the Jeep. I am just going to have an extra motor laying around and was trying to think of something to do with it.

 

I would also most certainly put in a cam among other things to give it a bit more power. Could this help?

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If I had a spare engine I would build a sand rail. or a massive go cart on steriods. lol.

 

A non modified L24 I would guess would make about a 100-110 hp with about at most 120 lbs/f of torque. Give you a idea of what you would start with.

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