best 4.0 to get for a project

[streetjeep2.5]

Getting my 2.5 running again, but want to start working on a 4.0 to put in its place, but want to get rid of all the computerization, so will probably at least put a better cam in it and will go with an after market carbureated system and header. May think of a mild stroker. Which year 4.0 for head flow, etc, would be best?

[Automan2164]

Carb? Why? The 4.0 fuel injection system is just new enough to be trouble free and reliable, and old enough that the average do it yourselfer can diagnose it with the simplest of meters and tools.

 

On that note, I have heard that the best blocks to build are the early HO's. So...'91-'95. They have a good block, and the head is already pretty decent. The Renix has a bit heavier cam, but if you are changing it out anyway, go with an HO.

 

Rob L.

[streetjeep2.5]

Was thinking carb simply because of getting rid of all the sensors and motors and everything run off of the computer because it appears leaning out due to a vacuum problem was what hurt my 2.5, and there are a lot of sensors in the vacuum system, and a couple I can not find new to replace just in case.

But, was researching this morning what it would cost to put a carb on it, and intake and carb alone would be almost a grand. So, that's out! Guess I will swap in a 4.0 and build it some:

 

http://www.angelfire.com/my/fan/stroker.html

 

or

 

http://www.bc4x4.com/tech/bryce/stroker/stroker.cfm

 

On Dino's site, I found:

 

'87...... XJ: 173hp at 4500rpm, 220lbft @ 2500rpm, redline 5000rpm

'88-'90 XJ: 177hp at 4500rpm, 224lbft at 2400rpm, redline 5000rpm

'91-'95 XJ: 190hp at 4750rpm, 225lbft at 3950rpm, redline 5250rpm

'96-'99 XJ: 190hp at 4600rpm, 225lbft at 3000rpm, redline 5300rpm

'00-'01 XJ: 193hp at 4600rpm, 231lbft at 3000rpm, redline 5300rpm

 

In 1996 engines received noise, vibration, and harshness fixes. The blocks were stiffened with extra ribbing, a main bearing brace was added, and lighter cast aluminium pistons were introduced to reduce cold start piston slap. Engines also received revised camshaft timing for more low rev torque.

 

Sounds like 96 and later XJ may be the way to go????

[DJM/78]

If you're looking for trouble free , than all factory is the way to go , either find a remanufactured 4.0 HO , or a new Jasper racing 4.0 HO .

I've heard allot of good things from people who wheel that motor . The wiring harness on the early HO are primitive enough for even me to figure out , without doing a 97+ swap ,

thats probably your best bet .

 

Strokers can be a nightmare if they aren't built correctly and in the field they can run hot , around here they have a pretty bad track record , most last about 100k before they need rebuilt

again and again . Mostly from what I've seen they are either going to a V8 swap or 4BT .

[terrawombat]

The best 4.0L in my opinion is one out of a '99XJ. It will include a NVH (noise, vibration and harshness reduction) engine with the '99+ horseshoe intake, a reliable, proven cylinder head, and the same old durable 4.0L block/bottom end that we all love.

 

Don't replace the computerized system with a carb. It will cost you more time and headaches in the long run. You're doing a complete engine swap - take the time to replace your vacuum lines so that you don't run into this supposed vacuum issue that hurt your 2.5L. There really aren't THAT many sensors on these engine - maybe 5 or 6 that have a direct impact on the way the vehicle runs and only one of those is vacuum operated (MAP sensor).

[JeepcoMJ]

The best 4.0L in my opinion is one out of a '99XJ. It will include a NVH (noise, vibration and harshness reduction) engine with the '99+ horseshoe intake, a reliable, proven cylinder head, and the same old durable 4.0L block/bottom end that we all love.

 

Don't replace the computerized system with a carb. It will cost you more time and headaches in the long run. You're doing a complete engine swap - take the time to replace your vacuum lines so that you don't run into this supposed vacuum issue that hurt your 2.5L. There really aren't THAT many sensors on these engine - maybe 5 or 6 that have a direct impact on the way the vehicle runs and only one of those is vacuum operated (MAP sensor).

 

 

late '99 has the horse shoe, and that's the bad head.

 

 

you want any high output block, the best head is the '95 head (higher nickel content). to make it easy, a '96 wiring harness (complete bolt-in, no newer dash required)...only need to splice over the tail wiring to the xj housing, and convert to the newer style column. the '96 is OBD2, which makes canning it easy.

 

to do a stroker, you MUST have the crank balanced out to the weight of whatever rods and pistons you go with. that is the only way to balance out the motor enough to NOT have internal vibration destroy it. there is no such thing as a poor man's stroker. period. if you think there is, don't build one, because you won't be doing it right.

 

 

 

you do NOT want any head from '97 and up. they have smaller exhaust ports and therefor more restriction with less power.

 

 

remember that wiring harnesses are engine and trans specific..4.0/auto are different from 4.0/5 speed. there is a 5 speed one in the junkyard by me (96) that's pretty clean. another junkyard has an auto. i can get what you need so far as wiring.

[terrawombat]

I was just speaking of proven reliability of the '99XJ head casting 0630 vs. the '00-'01XJ 0331 head casting.

 

My ideal stroker project will include a '00-01XJ block with NVH and new RMS design, cylinder head casting 7120, and '99+ intake.

[JeepcoMJ]

my late year '99 is an 0331 casting. just pointing that out.

 

the 0331 is the worst head you could get. constantly cracking and causing issues.

 

 

i'd build it the way I suggested. easiest for a weekend mechanic to do.

[87Warrior]

In all honesty, I think you would be money ahead (and have a smaller headache) to find a 91-95 XJ to swap the motor/tranny/t-case and fuel injection system from. This way you will also get the proper radiator and hoses for the swap. Then it would be just a matter of moving the engine harness to the MJ and adapting it to the MJ dash (or swap the XJ dash and adapt the bed harness to the XJ tail lamp assembly).

 

If you want a '92 4.0 long block to wrench on, I've got one taking up space in the barn (it was in my truck before starting the 99XJ swap).

[jpnjim]

There's no mechanical fuel pump boss on 4.0L engines,

so even if you remove all the electronics, and go carb, you still have to deal with a potentially unreliable aftermarket electric fuel pump

(the stock 4.0L in tank electric fuel pump has way too much fuel pressure for a carb'd engine, and aftermarket external mount electric fuel pumps don't expel heat well, so they have a higher failure rate than intank style pumps) .

 

You'll also have to retrofit a distributor that is not integrated with the 4.0L's ECU, since all 4.0L distributors are part of the Fuel Injection system.

 

 

If you really want to go carb, get a YJ 258, and bolt a 4.0L head on it, with an aftermarket carburated intake.

 

YJ 258's are the last of the 258 blocks, and they readily accept 4.0L heads (they use 1/2" head bolts, and the deck fits a 4.0L's water passages, without mods).

They also have the mechanical fuel pump boss.

 

Personally, I'd use the 91-95 style HO engine & computer, and carry a spare set of sensors if I was worried about failure.

[terrawombat]

my late year '99 is an 0331 casting. just pointing that out.

 

Strange. Did it have a dizzy or coil packs?

[JeepcoMJ]

my late year '99 is an 0331 casting. just pointing that out.

 

Strange. Did it have a dizzy or coil packs?

 

dizzy, with bosses for coil packs. real late '99 production...

[streetjeep2.5]

In all honesty, I think you would be money ahead (and have a smaller headache) to find a 91-95 XJ to swap the motor/tranny/t-case and fuel injection system from. This way you will also get the proper radiator and hoses for the swap. Then it would be just a matter of moving the engine harness to the MJ and adapting it to the MJ dash (or swap the XJ dash and adapt the bed harness to the XJ tail lamp assembly).

 

If you want a '92 4.0 long block to wrench on, I've got one taking up space in the barn (it was in my truck before starting the 99XJ swap).

 

Yea, probably what I shall do. IF it is still around after Christmas I know of a 91 wrecked MJ with a 4.0. I could swap everything in, including front springs, AC, and PS. I have no AC or PS right now.

And, no, I'm not gonna tell you where it is, so there!!!! :brows:

[87Warrior]

Trust me, my arms are full!

 

I also have the AC system and power steering stuff too. If you happen to miss out on that 91, give me a shout if you want the parts.

[streetjeep2.5]

Trust me, my arms are full!

 

I also have the AC system and power steering stuff too. If you happen to miss out on that 91, give me a shout if you want the parts.

 

Kewl! I shall if the becomes the case!