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91 4.0 HO in a 98 XJ

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My brother's 4.0 seized on him last night. Luckily just a few miles from his house, and I had just gotten to his house before it happened so I was able to push it home with my XJ.


I have a rebuilt 91 4.0 HO with about 50k on it. Will this be a direct dump into a 98? I know they had different cams, but is there anything else I would have to worry about?

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I'm putting a 98 4.0 block into a 91 MJ.....as for the computer issues, I agree. Some of the sensors in the intake manifold will swap...IAT/TPS sensor for example. Although these engines have different power steering mounting patterns on the intakes. You will need to use the 98 intake manifold to retain all the sensors, fuel injectors, fuel rail and throttle body, as they are different from a 91. Just swap all sensors from the 98 engine to the 91....it should be pretty staight forward.


Also the fuel pressure for a 91 H.O. is 39 PSI I believe and for a 98 it will be 49 PSI. 91 fuel injectors are supposedly rated at 21lbs/hr. A 1998 is rated at 23.3lb/s an hour...they have grey terminals on the injector.


Hope this helps!

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I wasn't planning on putting in any of the 91 wiring. I was going to retain all the 98 manifolds, sensors, etc. All that is fine. Something inside the motor seized. So all the 98 sensors would go into the 91 block? Would I have to swap distributors?



You also may want to be careful because a lot of state have made it illegal to put an older drive-train in a newer vehicle, so the next inspection may be a bit difficult. To get the truck to pass, unless the inspector is completely inept.. :redX:


No inspections.

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