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4.0 HO swap in a 90

NorCalChris

NAXJA Forum User
So im in the process of looking for a newer motor for my jeep. Im getting ready to head to the junkyard to scout. i have a 90 xj with the renix motor. ive found some good deals on the HOs around my area off craigslist. but none for the renix. im looking for something with low miles so the renix is going to be hard to find because they are so old.


(im sorry i havent searched yet, this idea just popped into my mind rigfht as im going to leave for the day)


how hard , or what is involved with the ho swap into the non HO vehicles. what modulars do i swap over etc,etc. is it worth it?

plz give advice and dont tell me to search. im going to as soon as i get home today. =]
 
OMG search... just kidding..

There's several people on here who have done this, myself included. You basically have two options, swap over the entire vehicle wiring harness and computers(the hard way), or adapt the newer motor to the Renix system. I used a 1993 4L HO in my 1987 XJ, and I run it on the Renix system. I have not heard of anyone adapting one of the newer OBDII engines, with the coil pack ignition, and I've seen little information about this. The engine I used should be mostly the same as all 1991-1995 engines. To run on Renix, you need to use all of the Renix sensors. You also need a Renix alternator, coil and distributor, and if the transmission is swapped also, you will need the flywheel or flexplate from a Renix in order for the Renix CPS sensor to work. The HO and later engines do not use a knock sensor, but some of the newer blocks (mine included) have a hole for it that only needs to be tapped to install, or not installed, as it will run with the sensor simply plugged into the harness. The most involved part of the adaptation is the TPS sensor on the TB. The options would be to swap the Renix head and intake manifold onto the HO block, or use the HO stuff and adapt the Renix TPS to the HO TB. Being in CA, if your XJ is street driven, your only option is probably swapping over the Renix head, intake, and header, as this is the only way to keep the EGR system working, and this is emissions equipment. At least you do not have to adapt the TPS in this case. I used the HO head and intake and adapted the TPS, as the 91-95 head is the best one, and the intake/TB is much better than the Renix units. If you are in some situation where you would be able to keep the better head and intake, and trash the EGR system, you can either fab an adaptor (mine's shown on the forums somewhere) or buy one from Hesco.

So, unless you decide to do this swap "hardmode" and swap the wireing/computors, I should be able to provide usefull information for you.
 
thank you. im still debating wheather or not i should rebuild my motor or what. so. we will see. i will definetly ask you for questions. heres my first. as far as i know the ho system is just heads and up. the block its self is the same. so i guess by switching over to an ho block. im just replacing the bottom end, which is nice, but i think a newer engine is in order. i just wish i had the money to do a stroker.


im going to look into rebuild kits and see what that costs opposed to a newer engine.
 
As far as I know, the major mechanical difference between the Renix 4.0 and the HO and later 4.0 is the head and intake. I have heard that the camshaft was made different in the HO, to compensate for lack of EGR system, although many sites selling replacement and upgraded camshafts list them as being for 87-95 or even just 87+. I've been unable to find good technical information about actual differences between Renix and HO stock camshafts. So I would say, the head and intake are the main differences, the only difference in the block would be the lack of a threaded knock sensor hole, and (at least in 91-95) mounting holes for the coil. I don't remember if the mounting for the alternator was different, but I did somehow get the Renix alt to attach to the HO block, just don't know which parts I needed to swap to get it done.
 
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