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Anyone done a 4 cyl to 6 cyl conversion?

92stroker

NAXJA Forum User
I have a friend who has a 4 banger that is getting tired. He wants to upgrade to a 4.0. What does he need, besides the 4.0 and ECU? Are there any gotcha's? Are there any good links? Does anyone make a simple wiring conversion? I looked at painless, but did not see anything on thier web site. Any input would be appreciated.


92stroker
 
A lot depends on what year your friend's XJ is, and what year donor engine and electronics he plans to use. If his XJ is an 84, 85 or 86, the 4.0L won't fit physically (without fairly major sugery) so he should forget the 4.0 conversion. If his XJ is an '87 or newer, the 4.0L will fit and he just needs to do the work.

There is no conversion wiring harness available that I'm aware of. CheapXJ did a 4.0L transplant into a 4-cyl MJ, and he just moved the entire wiring harness over from the donor vehicle.
 
I swapped in a 4.7L stroker instead of my 2.5L in my 85 XJ. It is a ton of work on the earlier vehicle. On an 88 and later it is a lot easier due to the sheet metal differences. The swap means changing everything under the hood. The easiest wiring is to swap everything including the complete wiring harness under the dash. The tranny is different and won't bolt up and you wouldn't want to due to the increased torque. The early 2.5L also used an NP207 tranny. You would ideally need to swap in an NP231 also. Both drive shaft lengths change an you have to move the cross member back about 4 inches.

It is doable but unless you just like doing things the hard way, it would be easier and probably cheaper just to sell the old one and buy a newer model.
 
old_man said:
It is doable but unless you just like doing things the hard way, it would be easier and probably cheaper just to sell the old one and buy a newer model.

Or, if it's an early carburetted or throttle-body injected 2.5L, do as Ghost did and swap in a rebuilt "2.5L "HO" with the newer multi-port injection, maybe add a Mopar Stage II or Stage III cam, and have fun.
 
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