Thanks for the responses. So far it looks like anything '87 and up will interchange. So what are the major differences? '91 and up they went to the HO version (177 to 190 hp). What changed in motor? Dave, you mentioned a cam change, is that the only difference?
To give some background on why I am asking....
- I have an '88 with a tired engine (305,000 miles) and I am buying a '93 with a blown engine
So in theory, I could pull any year 4.0 and stuff it in the '93 (or '88) as long as I change out the intake/exhause/injection; right? Am I missing something?
I found this while checking to see what the differences were:
The 1987 RENIX 4.0 made 173 hp (129 kW) and 220 lb-ft (298 N·m) of torque. In 1988 the 4.0 received higher flowing fuel injectors, taking output to 177 hp (132 kW) and 224 lb-ft (304 N·m) respectivly.
In 1991 Chrysler Corporation, then the owners of the Jeep brand, redesigned the RENIX engine control computer and raised the intake ports approximately 1/8" for a better entry radius. Chrysler also enlarged the throttle body and redesigned the intake and exhaust manifolds for more efficiency, and the fuel injectors were once again replaced with higher flowing units. The camshaft profile was also changed. The net result of all these changes was an engine that made 190 hp (142 kW) and 225 lb-ft (305 N·m) of torque. Badging on Jeeps equipped with this engine read "4.0 Litre HIGH OUTPUT". The new cam profile combined with altered computer programming eliminated the need for an EGR valve and knock sensor, but make the engine more sensitive to alterations, especially where emissions are concerned.
Small changes were made to the cylinder head for the 1995 model year. In 1996, the engine block was redesigned, and a new strengthend unit was then used. The new block made use of more webbing cast into the block, and a stud girdle for added rigidity of the crankshaft main bearings. The cylinder head was also again changed around 1998 to a lower flowing, but more emissions friendly, design. Engines installed in 1999 Grand Cherokees carried the Power Tech name, which was subsequently passed on to 4.0s in all Jeep models
------------------------------------
So you can put most any 4.0 into your rig as long as the control and injection system goes with it. If you put a newer engine into your 88 you will need to used the Renix control and intake manifold, or you can take out all of the wiring from the 93 and swap it into the 88 with a newer motor if you want the extra power. If you put an older motor into the 93 you will need to use the intake manifold and all of the injectors from the 93.
