4.0 rebuild

[Ptm]

My 06 Rubicon runs great but will someday need a rebuild. I’d like to buy an engine and do a rebuild in my free time and will eventually swap in when needed. My question is about interchange between years. Can I buy any Jeep 4.0 and rebuild the short block and just swap my accessories, head, etc. when the time comes? Is there one variant of 4.0 that would be better to look for? Thanks in advance!

 

[bromel]

Unless you want a nightmare of a project that involves cutting and welding engine mounts, do not use a 1997-1999 TJ engine. (Some very early 2000 engines use the older design, too.) Do not use any XJ Cherokee engine for the above reason. (Yes, even the newer 00 and 01 Cherokee 4.0s are no bueno.) You can generally use any TJ engine from 2000 on that has the newer 0331 head design. You can also safely use any 99-04 WJ engine.

2000 and 2001 engines use the non-TUPY 0331 head, which is prone to cracking. However, since you are planning to swap your 06 TUPY head over, and since you are planning a rebuild, it probably doesn't matter. Just know that any junked 00 or 01 engine may have a cracked head, and therefore bad bearings due to coolant contamination.