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98 4.0 into 91... issues?

bob-n

NAXJA Forum User
Location
SE WI
Will begin swapping a low-miler '98 4.0 from a donor XJ into my old '91 Briarwood tomorrow, replacing the tired stock 4.0. Is there any somewhat simple way to use the '98 FI stuff or will I just save myself the impending grey hairs by using the '91 manifold? I see the difference in the fuel rails and other completely obvious items, but I'm guessing there's a lot more to it than that!

Thanks,
Bob-n

...the artist formerly known as Bob-bee
 
Just install the '98 long block and bolt on everything from your '91. The only problem you'll have is where to put the sending unit for the coolant temp. gauge because the '98 head doesn't have a port for it. I suggest you drill and tap a hole in the t'stat housing and put it there.
If your '91 has the AX15 5-speed, you're going to need a different pilot bearing at the back of the crankshaft to accomodate the '98 crank. Advance adapters have the one that you'll need for the AMC crank with 1.81" outer diameter and 0.59" inner diameter.
 
Thanks Doc...

Is there anyway to use the injectors from the '98 motor? (they only have 50K compared to 190K on them) I kinda figured the easy way *was* the easy way...
 
The '98 injectors are designed to run at 49psi so if you use them, they'll be operating at only 39psi so you may have problems with inadequate fuel atomization.
 
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