4.0 HO head and related componets on a 89 4.0?

[wildman4x4]

Hi all,

Well since the weather is warming up I can start thinking about working on the Comanche finally. I have a 92 4.0 HO head with the wiring harness and computer that I'd like to swap onto my 89 4.0 engine. I know the head will just bolt on but can I just use the stock wiring and just plug the 92 computer into it? The only thing I don't have anymore is the exhaust manifold as we used it on my sons Cherokee. So I plan on getting a good aftermarket header for it. What kind of performance gains would I get by adding the head?

Thanks for any help.

[gogmorgo]

Stock wiring is a no. Different pinouts on everything even if the plugs are the same. As for HP gain? Probably not much noticeable on the butt-dyno. Maybe 10hp, if that.

[wildman4x4]

Ok so then I guess the next question would be is it even worth it to go thru all the trouble to try and change the wiring and such? I know I can just install the HO head and then put all the stock equipment back on it. Is that worth doing?

[Marine1Texas]

The amount of work I think it not worth it. in the end your talking about hp at your top end. no torque increase at all. Basically the easiest thing to do is get your throttle body moded with bigger butterfly and better intake.

[cruiser54]

My 2 cents first, with instructions second.

 

HO myth buster

 

 

Renix in 90 made 182 HP. HO in 91 made 190 HP. That's 8 HP difference. 

 

HO only made more HP than Renix at higher RPMs and not a bit more torque. HO had 58 mm throttle body versus a 52 mm throttle body on a Renix and also had a better design header. See where I'm going with this?

 

The whole 8HP was not mostly from the head, but from the bigger TB and better exhaust manifold.

 

Put a 60mm TB from www.strokedjeep.com on your present head, eliminate the "crush" in your headpipe with proper re-routing, and go for it. 

 

HO stands for Highly Overrated.

 

 

Cruiser’s HO into Renix Swap

 

This swap is easier than some will lead you to believe, generally those who have never done it. Those of us who have done it, like myself, will share with you the things that need to be done for a successful swap. Just think of it as swapping in a long block.

 

The HO and Renix have some differences but none that can’t be overcome very easily.

 

Any HO engine from an XJ or ZJ through 1999 can be used. One running change was that the rear of the head was no longer drilled and tapped for the temperature gauge sender beginning in the 96 model year. The sender can be relocated to the threaded hole in the thermostat housing taken from the HO engine. You’ll have to extend the wire to that location. Some brave souls even drill and tap the HO head for the sender.

 

You will be using the intake and exhaust manifolds from your Renix, along with all your sensors and wiring. Since the intake ports of the HO are slightly different, you use the Renix gasket. Exhaust ports are identical.

You will need to use your Renix distributor as it is different than the HO because they use different fuel management systems. The  flywheel or flexplate from the Renix must be used so your CPS gets the correct signals. The valve cover from the Renix allows you to keep your CCV system intact and requires no modifications.

 

The HO block will have a plug in the coolant galley on the driver’s side of the block, closest to the front, which needs to be removed so your Coolant Temp Sensor can be installed in it’s place just as it is on the Renix. It requires a 5/16” square drive or a modified 3/8” drive that has been ground down to fit. Do this before installing the engine.

 

As for the knock sensor, which is located just above the oil pan on the driver’s side of the engine about mid way, all the blocks I’ve seen are threaded for it. If not, I’ve heard they may be drilled but not tapped. Tap the hole if that’s the case.

 

 

Revised 03/28/13

 

 

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