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Old June 25th, 2009, 04:14
codysown's Avatar
codysown codysown is offline
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93 4.0 HO to 90 Renix

I have bought a Wrecked 93 Cherokee Country with 200,000 miles. Started right up after sitting in a garage for 2 1/2 years. Smoked a bit at first, but cleared up by the time I drove it across town. This may have something to due with the old gas also.

I have a 90 Cherokee with a 3 inch lift on 32's that runs but is getting fairly weak. I would like to pull the HO and put it in the Renix with the renix injection system. I dont feel that the HO adds enough to deal with all the picky sensors. I would be swapping everything that fits, including the AW4 and Tcase.

I plan on doing a refresh of this motor, ie. rings, seals, bearing and gaskets prior to putting it in. What head would be best to use and what modifications do I need to do to it to make it work. Would I be better off using the Renix head? As always, trying to do on a budget, so not looking to do any expensive performance boosters.

I have read somewhere that the HO was around a 15 HP gain over the Renix, and that using this head can gain you back 10 HP over a stock Renix. I do have the Ford injectors installed on my Renix.

I would like to hear from some of the experts on here about what the best avenue is going to be for me.

Thank you in advance for your advice.
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Old June 25th, 2009, 04:18
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codysown codysown is offline
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Re: 93 4.0 HO to 90 Renix

I would like to add that the 93 HO runs very strong and sounds very smooth for the mileage. Oil has seeped out in places and the seals are leaking a bit. Compression seems to be good, however I have not pulled the plugs or really looked at it very much. I dont want to start tearing into until I have a good starting game plan on what path I want to take with this. Maybe it would be easier to just pull my Renix and do a refresh on it.

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Old June 25th, 2009, 06:51
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TiRod TiRod is offline
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Re: 93 4.0 HO to 90 Renix

What can be recommended and whether you get periodic emissions testing can be important.

An HO is the better motor, specifically for the improved head. It needs to go on the same block to reduce the head gasket complications. You may need to tap the block for the Renix knock sensor.

The HO cam is actually a lesser performer, Renix the better. HO cams have so much overlap the EGR valve could be eliminated.

The economic cost of an overhaul should be totaled up. Your best bet may be to just install the HO as is, depending on mileage and a compression test. Then you could put real money toward a nicely built stoker - a 96 up block, HO head, 99 up rainbow intake, graphite skirt pistons, and a good 258 crank and rods. 22 pound injectors become a requirement then - but it all works with Renix. Some say it's easier to tune a stroker in Renix than OBD. Mods are certainly easier and control more with less negatives, like CEL's constantly popping up.

Compression testing both motors would deliver some important data that will help decide.
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Old June 25th, 2009, 10:26
joe_peters joe_peters is offline
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Re: 93 4.0 HO to 90 Renix

If it ain't broke...?

200K miles on a 4.0 is just past it's initial break in period. Check the compression, if good run it for 100K + miles.
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Old June 25th, 2009, 13:34
Slip Kid Slip Kid is offline
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Re: 93 4.0 HO to 90 Renix

Interesting, I put a 4.0 HO, AW4, and NP242 from a wrecked 1993 Cherokee Country with 200k into my 87 Cherokee. To run Renix ignition, every single sensor needs to be swapped, and the AW4 must have the Renix flexplate installed into it. To use the HO intake/TB the TPS must be adapted to work with the HO TB, you must also get rid of the EGR system, which is emissions equipment, so that may be a promlem for you. When this is done you must either use the exhaust header from the HO, or cover the EGR hole on the Renix unit. The only way around adapting the TPS and deleting the EGR is to swap the Renix head onto the HO, and use the original manifolds. This of course removes the biggest advantaqge to the HO, but will leave you with a functioning, legal engine nonetheless. You are probably better off with the Renix camshaft if you go this route, as the HO shaft was made worse performing to allow the deletion of the EGR system.

My HO block had a hole in it already for the knock sensor, but it needed to be tapped, I don't recall the size, but it was not something typical, I belive it was fine thread. You will want to use the fuel injectors from the Renix, reguardless of witch intake/fuel rail you use. I kept the HO injectors for a long time, and got ~10 mpg. As you have the Ford ones already, you'll def want to use those, the HO units flow too much fuel for the Renix electronics. One of the temp sensors, i think it was the one in the block, had to be installed into the HO tstat housing as there was no hole in the block, it fit fine where I put it. Good luck and don't forget to swap the flexplate, or it will not even start.
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