I have a 1987 XJ with the 4.0 I6 and it dropped a rod through the oil pan last week. I use it as a hunting vehicle and I really don't want to drop alot of money in it so I'm gonna try to find a used engine. My question is are all 4.0s the same? would one out of a 95 grand cherokee be the same? If not what years will work?

 

87-90 4.0 is the only direct swap

91-98 MIGHT work, there are minor differences in the block. maybe someone else can chime in

 

I put an 89 short block into a 91. only thing I found different is the bolt holes for the coil used on the 91.
In my experience a newer short block will have any mounting bosses that were on preceding years. But not the other way around.
Meaning you should be able to use any I6 block from 01 down to 87 in your rig but not an 86 block. If they made one.......

 

yep and i know the 2.5 work the same way from what i've seen

 

Next question.. What would I need off my old motor to put on the new one?

 

i heard that 96+ is the H.O. motor and requires a diff. ecu and wiring harness if its a short block find you will need to use your old head,, valve cover,, new oil pan,, wiring harness,, intake mani,, exhaust mani,, intake possibly your crank caps (if it didnt come with any or if they are worth reusing) ,, and the snorkal looking thing towards the back i never knew what the name was but it looks like a snorkal.. thats all i can really name off the top of my head and if you are looking to reuse any parts off your old motor check for excessive wear and scores and all that jazz
good luck!

 

You can use any 4.0 long block from 87-95,you can actually use them through 99,but there was changes in 96 and 99,but not big enough to stop you from using them. gc engines are the same except for some reason they use different mounts,but just the rubber insert not the brackets.
If you buy a motor 91 or above you will need to use your intake,exhaust,flexplate,dist,basically all you can use is the longblock from a 91 or above. I have a 91 in my 89 and all I used was the longblock,I had to pull the motor back out to put my old flexplate on,the tone rings are different and will not work.
The 91 and above are the h.o motors and the intake and exhaust ports on the head are larger than the earlier motors,so your intake and exhaust manifolds are a little smaller and cause a restirction,I do not notice much lack of performance but it sure is not the same output as the h.o.
But I just bought a 258 so I can build a stroker next month.

 

x2, i have a 96 engine in my 90. like "abovetimberline" said long block. strip all the good stuff from yours and put it on the donor engine.

 

Well as far as I know everything is good on mine except the #2 rod is sticking through the oil pan. It ran fine up until that point.

 

ive got a 96 in my 89... and i just went through all kinds of crap... the dummy who did it used the renix stuff on the HO block and heads... yeah they bolt up but the ports dont line up... found this out after starting a 99+intake mod... so i ended up swapping the intake... Throttle body... throttle linkage... throttle brackets... fuel rail... TB sensor wires were all goofed up... PITA... was planning on doing a write up but im not sure i got the TPS just right yet... if i was u i would use a motor from 90 down... NOT a H.O. unless you feel like swapping all this stuff also.. oh and a ZJ's fuel rail and fuel lines are different then a XJ and the 96 zjs rail will b different then ur XJ's... just go with a 90 or below man... plenty out there... unless you want to deal with all this... look up renix to H.O. swap on google... you will see... better off finding a newer model with a bad tranny and swapping ur good tranny in it... lol

 

The only problem I had was the front bolt hole on the intake,just rounded it out a little and worked fine,the other lesson I learned was flexplates are not the same,the hard way.