non H.O. to H.O. engine

Hey I have an 88 Cherokee with a dead non H.O. 4.0 motor and was wondering if I could swap a newer High Output motor in my older Jeep or if there a common issues that arise with this swap such as electrical or cooling issues. your feedback would be greatly appreciated

Cooling isn't an issue, but electronics can be.

However, since the lower half of the engine is essentially the same, why not rebuild the lower half, put on a newer head, and come out farther ahead than you were when you started? Apart from the electronics (deletion of the knock sensor, changed the HEGO sensor, HO Tbody/TPS different, and a few other things I just don't feel like looking up right now...) the principal difference between the two engines is the cylinder head. The blocks are mechanically the same all the way from 1987-2001, with the only differences really being the knock sensor boss going unmachined (starting in 1991) and the addition of the main stud girdle (beginning in 1994 - but can be added to any 4.0 if you get the right main bolts.)

The cylinder heads were changed a couple times, with casting #7120 being accepted as the best.

Also, you could rebuild your bottom end, and try a copy of the new aftermarket head that's out now - you can get them from quite a few people (but HESCO started it...) The newer head is supposed to breathe even better than the 7120, accepts roller or stamped rockers, and the aluminum allows/requires you to run high compression - which can translate to more torque. I also like the fact that they made the lifter bores bigger - you can pull lifters without pulling the head! (that was a big point when we were discussing a "clean sheet" cylinder head in, say, 1Q2001 or so...)

Mechanically, there isn't much difference between RENIX/OBD-I/OBD-II engines - the dimensions are the same (inside and out) and the cranks, pistons, and heads interchange. The HO intake and exhaust won't bolt onto the RENIX head - so you just swap the whole thing all at once, and call it done. The exhaust pipe comes up in the same place (probably same flange, to boot) and you get the better-flowing OBD intake manifold and throttle body.

It woud take a little work, but you don't have to swap as much in the way of electronics...

5-90

I am looking to replace my 89 4.0 with a 94 4.0, so they 89 intake will NOT bolt to the 94 4.0? I have been searching all day for this info and have not had luck with it. I seen lots of reference to using search but I guess I'm not using the right terms. Looked at the cherokeeamerica site but I am not interested in switching the electronics, just the long block. Any help on the search terms covering this?

Search terms used: 94 4.0 to 89 4.0, non HO to HO, newer 4.0 to older XJ, new XJ motor to Older XJ

A friend of mine just lost #6 cylinder in his MJ this weekend. We swapped out his H.O. for a Non H.O. today. The intake and exhaust from the H.O. bolted right on to the Non H.O. head no sweat. Not to mention the motor we pulled out was not the original. The original had locked up a couple years back. When he got it we swapped in a 94 H.O. motor from a wrecked XJ. Replaced that motor today with a non H.O. from an 90 XJ we parted out awhile back. Worked fine for us. Just my .02 cents.

The manifolds exchange with minor grinding to fit. (a bit of notching) but the egr tube between intake and exhaust needs slight lengthening. (tube cutter and tube coupler worked on mine)
Make sure you use the CPS and flywheel for the system you are going to run, or it won't start! (Renix has micro AC signal and HO uses DC halleffect signal)
Now if someone could help me with the '93 Grand Cherokee Alarm/wiring system I'd greatly appreciate it! <G>

Hate to rob a thread but, if you figure anything out on your 93 ZJ. Let me know I have a 95 that I would live to eliminate a security on.

i recently stumbled upon some chrysler tech that stated you can unplug the anti theft module while the engine is running to disable it but i dont know if it applies to the jeep......is the module in the pcm on these?(it worked dandy on the dynasty junk i was working on)

You could get away with using a newer complete engine and install the Renix electronics to it, use the old distributor, sensors (drill/tap the knock sensor hole), fuel rail, and throttle body (use an adapter) and still come out without too much fabrication necessary. Also, the thermostat housing is different. What did I miss...