so i have to replace my whole engine in my 98 cherokee limited... just wondering which motors will fit... does it have to be the same body type (97-01)? or can the older model engines fit.. its the 4.0 L straight six

 

You can use any longblock from any year,however in my opinion you should stay within the years that is compatiable with yours and that is 96-98,stay away from 87-90 as they are not h.o motors.
There have been changes to 4.0 over the years and even though they were in most cases slight,it will effect how they run. the changes took place starting in 91,motor was upgraded and now considerd to be a highout put motor,with different intake/exhaust,cam,injectors,etc.it was changed again in 96 with a different head and different cam,it was changed again in 99 with different head and intake. Electrical connectors have also changed. If you want a direct replacement,96-98,if you want a longblock to bolt your stuff to,then i would stick with 91-98,but you can use any longblock if you had to.
In my opinion,96-98 will be a direct fit and no issues.
The other thing to keep in ming is 96 the block was upgraded and more webing was added to the block to make it stronger.

 

It best to use a engine from 1996 to 1999 same ignition set up, you can use 2000 to 2007 you will have to swap over electrical

 

keep it 97-99 stay away from the DIS ignition unless you want to swap a bunch of stuff......

 

hey timberline... i found a bunch of 96 engines, are you suggesting the 96 is one of the best? or at least better then 97 or 98?

 

In 96 they added webing to the block to make it stronger,so 96 and newer are the same,the changes after 96 have to do with the head and intake,stay with 96-98
in 99 they had the best intake because the head flowed so bad they improved the intake to make up for hp they lost with the head,all in the name of emissions.