are all 4.0s the same?

really, for all the years jeep made the 4.0 are they all the same engine with all the same parts?

thanks

NO..

Dyno has some great spec's on his site..

Jeep 4.0 Performance

You get some pretty good results by searching before asking questions like that as well...

spazegun2213 said:

really, for all the years jeep made the 4.0 are they all the same engine with all the same parts?

thanks

Click to expand...

The basic architecture of all the 4.0's is the same but there were minor detail changes made to the engine over the years, resulting in different HP/TQ outputs. My site has all the details.

ok, all the site tells me are some intresting tid bits about HP, i realy want to know about the internals, like intake, headers, pistons, etc.

sorry, as i said I'm a newbie and dont know how to word my questions correctly.

spazegun2213 said:

ok, all the site tells me are some intresting tid bits about HP, i realy want to know about the internals, like intake, headers, pistons, etc.

sorry, as i said I'm a newbie and dont know how to word my questions correctly.

Click to expand...

Don't worry, not all of us are like Yucca-man, I do tell peolple to search, but I usaully try it myself first. Sometimes it works really well, but if your don't have the right keywords or you are screwed.

The earlier XJ's had the Renix intake system, the later years has the Chysler High Output system. I believe the change over was in 91'. There is also a change at the end of the production of the XJ in 99-00.

The blocks are basically the same as far as I know, the only differences are intakes, headers and timing/computer systems. You should be able to find the details in a search. Try renix or HO, they should help in the search.

Intakes and headers are not "interrnals."

There are too many variations to go into from memory, but in general there are three variations on the 4.0L.

First was the 1987-1990 non-HO. This used a Renix (Renault-Bendix) electronic multi-port injection and it had a knock sensor to help control timing.

In 1991 Chrysler replaced the Renix injection with a Mopar injection and OBD-I compliant ECU. The knock sensor disappeared. Bore and stroke remained the same. Head and intake manifold were redesigned, throttle body was different. Some sources say the camshaft grind was different, others do not confirm this. I don't know.

In 1996 the ECU was changed to OBD-II compliant. As far as I can recall the engine remained pretty much the same.

In 1997 the block casting was revised for more stiffness and a "girdle" was added to the main bearing caps to keep everything lined up.

In 2000 the ignition was changed to direct coil-on-plug ignition and the exhaust manifold was redesigned. Don't know if the cam grind was revised.

Pistons were redesigned a couple of times. In the early 90s (don't know which year) Chrysler shortened the piston skirt to save weight. This resulted in piston slap and noisy engines, so a few years later Chrysler changed to a new piston with a graphite or teflon coated skirt to reduce the noise. Pistons from all years will work in blocks from all years. I believe they all have the same compression ratio.

Why don't you give us an idea what you want to do so we can provide some direct advice, rather than asking us to recreate the entire history of the modern world in 25 words or less?

ChuckD said:

Don't worry, not all of us are like Yucca-man, I do tell peolple to search, but I usaully try it myself first.

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Pppbbbfftttt.... What would you search for if you were going to do it for this person? Terms like vague and engine and differences? Or maybe unwilling and search and myself... face it, the original question was just too damn vague and yet frequently discussed in these forums.

Yucca-Man said:

Pppbbbfftttt.... What would you search for if you were going to do it for this person? Terms like vague and engine and differences? Or maybe unwilling and search and myself... face it, the original question was just too damn vague and yet frequently discussed in these forums.

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My point exactly, it is easy just to say go search, but I have found it isn't just that easy. If you thought his question was vague, then ask them to be more specific, or better yet, don't answer if you don't know.

Since you don't know what he was looking for, and I don't know what he was looking for...and we haven't seen evidence that the original poster knows what he was looking for, I said search. That way, the original poster can play around to his heart's content with whatever terms they feel justified using.

Umm.. sorry for causing any anger.... Yes i should search but (I'll admit) I'm a little lazy and a search for engine and other "keywords" means wading through a TON of stuff thats not what i want. I didn't mean to cause any inconvience (sp?).

Anyway, I'm looking to build a stroker from parts (best way for more power). thats why i was wondering if there were any major differences. sorry about calling the intake a "internal" when its not, sometimes i put the cart before the horse.

As for knowing what i want... how about AWD and 300hp... oh wait thats a Subaru STi and they are 30K!!!! So I'll stick with something a little cheaper... my xj will do for now!

thanks again!!

spazegun2213 said:

Umm.. sorry for causing any anger.... Yes i should search but (I'll admit) I'm a little lazy and a search for engine and other "keywords" means wading through a TON of stuff thats not what i want. I didn't mean to cause any inconvience (sp?).

Anyway, I'm looking to build a stroker from parts (best way for more power). thats why i was wondering if there were any major differences. sorry about calling the intake a "internal" when its not, sometimes i put the cart before the horse.

As for knowing what i want... how about AWD and 300hp... oh wait thats a Subaru STi and they are 30K!!!! So I'll stick with something a little cheaper... my xj will do for now!

thanks again!!

Click to expand...

That's an XJ too . Get the supercharger kit and get the np242 transcase and there ya go. 300hp and fulltime 4wd.

what is a np242 transcase ?

COOL! thats anothing to add to my list.....

spazegun2213 said:

Umm.. sorry for causing any anger.... Yes i should search but (I'll admit) I'm a little lazy and a search for engine and other "keywords" means wading through a TON of stuff thats not what i want. I didn't mean to cause any inconvience (sp?).

Anyway, I'm looking to build a stroker from parts (best way for more power). thats why i was wondering if there were any major differences. sorry about calling the intake a "internal" when its not, sometimes i put the cart before the horse.

As for knowing what i want... how about AWD and 300hp... oh wait thats a Subaru STi and they are 30K!!!! So I'll stick with something a little cheaper... my xj will do for now!

thanks again!!

Click to expand...

Dr. Dyno is our resident authority on strokers. For the info you're seeking, you really need to log onto the Strokers' e-group at Yahoo.com. Dr. Dyno can get you on there -- my access got screwed up a couple of years ago. Drop him a PM and ask how to access it.

And be sure to brush up on terminology. You get better answers when you ask good questions. As I commented above, things like intake and exhaust manifolds are not "internals."

BTW -- it might also help to define what you want to use this for. Increasing the stroke is a way to gain some power, but not great huge gobs of high RPM horsepower. The primary benefit of increasing the stroke is low RPM torque, but all things being equal any increase in cubic inches should gain some horsepower.

If you're looking for street and drag race type horsepower, it would probably be more cost effective for you to just buy a good cam kit and a set of larger injectors, possibly coupled with one of those aftermarket chips.

Right now all i can get into is the small stuff, a stroker will take a ton more time, investigation, and money. I'll keep it simple till the only other way to add power is by stroking it. As for what i want in the jeep... its simple... to go faster! I love the the 4.0 and since stroking is cheaper than a supercharger stroking will be my only option.

I have a long list of parts that I would love to put on my XJ but my wallet and watch are keeping me back.

The point of this post was to learn about the engine (best place to start i guess) i figure I'll dive into it with small stuff and the big stuff will come last. I do really appreciate how understanding you all are and I'll try to become proficent in questions so you all understand what I'm trying to ask.

You're missing the point. "Faster" to me means that you want a top speed of 120 MPH instead of 110 MPH, but I suspect that for you it means you want more/quicker acceleration. Strokers increase torque more than they increase horsepower. While torque increases also help acceleration, the increase is generally off the line, not through the full RPM range. An engine with a longer stroke just doesn't wind up as quickly as an engine with larger pistons and a shorter stroke. When AMC/Jeep introduced the 4.0L they actually REDUCED the stroke and the displacement from the previous engine, which was 4.2L (and that's why we can build the strokers). Why would they do that? Because they felt people wanted to feel quicker acceleration, and a shorter stroke/larger bore was the way to achieve that.

For what I think you wish to accomplish, I still think your most cost-effective solution is a cam kit, injectors, and maybe a Jet chip. If you really think you need a stroker, go back to Dr. Dyno's web site and review the several stroker "recipes" he has posted. If I remember correctly, with each one he gives you an idea of what kind of horsepower and torque that engine should produce.

Ok it's my turn to question you Eagle. I specifically remember the machine shop telling me that the pre 91 4.0 used different pistons which will yeild a higher compression ratio in the newer engine due to a smaller combustion chamber on the HO head. They actually suggested using these pistons though to bump up the compression a bit. This would probably require the use of premium fuel though. (ok with me I already have to buy the good stuff for my car). THis was a reputable shop with over 30 years in the business, are they wrong?

If you want to know how the internals changed on the 4.0 engine over the years, here goes:

1. Camshaft. It's the same on all 4.0's from '87-'95 (HO and non-HO). The cam timing was adavnced in '96 for more low rev torque and from '99 onwards, a new dual pattern cam with a longer exhaust duration was used to compensate for the poorer cylinder head flow. The cam sprocket and retaining bolt are also different from '99 onwards. Aftermarket performance cams can only be installed on 4.0 engines up to '98 unless you convert the '99+ cam sprocket/retaining bolt to the earlier type.

2. Pistons. Again, these are the same from '87-'95. In '96, lighter weight graphite-coated skirt pistons were introduced to reduce piston slap but they didn't fix the problem completely. The piston dish volume on all 4.0 pistons is 13.1cc.

3. Cylinder heads. The '87-'90 had low port heads that din't flow very well. The '91-'95 heads improved on these by having the intake ports raised. The '96-'98 heads are almost identical to the '91-'95 versions except that they don't have a port for the coolant. temp. gauge sending unit. The '99+ heads have much smaller exhaust ports that don't flow as well. All the 4.0 heads have ~57cc combustion chambers and the CR of all 4.0 engines is 8.8:1.

4. Crankshafts are all the same except that from '92 onwards, the pilot bearing hole was enlarged to accomodate a new pilot bearing for the larger diameter input shaft of the AX15 5-speed tranny.

5. Block. The '87-'95 blocks are essentially the same. The only difference is that the '87-'90 blocks came with a knock sensor. The ribbing on the crank main webs was beefed up on the '96+ blocks and a main bearing stud girdle was added to reduce NVH.

If you want to know what parts are needed to build a stroker, I have a comprehensive write-up about mine here.

Dr. Dyno said:

4. Crankshafts are all the same except that from '92 onwards, the pilot bearing hole was enlarged to accomodate a new pilot bearing for the larger diameter input shaft of the AX15 5-speed tranny.

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What changed at that point? The AX-15 was introduced in mid-89. Great list though; that's getting saved.