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So the engine in my 1990 wrangler has gone over hill. The cylinders are scored and they are already bored .060 over. A good friend of mine has found a 1998 engine still assembled (it was removed because the owner put a bigger engine in). It also has the 5 speed transmission if I'm not mistaken the ax5 and transfer case with it. its quite a deal, but my question is would the block be able to fit in the 1990 wrangler? If I get parts for it would I need 1998?


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Sinisterwillys1940...The 1998 engine is MPI and not TBI like your 1990 engine.  I combed the internet for long block interchangeability and found the most information at the ATK Vege Catalog.  On page 89 of their PDF catalog, you will find the Jeep 150 2.5L four-cylinder listed.  The rebuilt long blocks (block assembly with cylinder head) break into four distinct listings:


There are differences noted between these engines and applications.  See the footnotes indicated for your 1990 2.5L TBI engine replacement and the 1998 2.5L MPI engine.  This tells what works and what doesn't.  The two significant groups are 1987-96 and 1997-2002.  Within these groups, the changes appear to be the camshafts, and the later cylinder head does not offer a temp sensor port at the rear of the cylinder head like your 1990 head uses.  

If you can determine that the rest of the long block is the same, you may be able to make this swap without a lot of trouble, swapping over your 1990 TBI intake and exhaust systems, the 1990 distributor, ECU and original peripheral parts.  It would be much more involved to convert to the 2.5L MPI system, which would include everything from the fuel pump to the PCM, engine wiring harnesses and the MPI fuel delivery and EVAP systems.  Use just the 1998 2.5L engine long block (block assembly and cylinder head).  Make a provision for the temp sensor and other differences. 

A hint:  The late 2.5L MPI likely uses the temp sensor in the thermostat housing like the 4.0L.  You may be able to adapt your 2.5L TBI temp sensor to the late thermostat housing port.

See the ATK catalog and judge for yourself.  The 1998 2,5L transmission is an AX5, the transfer case could be an NP/NV231 with a different input spline count than your current AX5 unit if you have the NP207.  Is your transfer case a 207?  You could swap the 1998 2.5L engine, AX5 and NP/NV231 into your chassis.  Match up the TC output splines and the slip yoke splines on your rear driveshaft.




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