Renix Head on HO block?

Can I swap a HO block into my 89 and use my renix head and keep everything else the way it is. I would want to reuse the renix head because I recently had it gone through and machined and I know its good to go? I'm thinking of going with a HO block because I have a better chance of finding one with low miles on it.

Yes. What year block?

cruiser54 said:

Yes. What year block?

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I was going to look for a block from years 91-96

Will I need to worry about the knock sensor and I think the block temp sensor since my wiring harness is set for those and an HO motor doest have those sensors.. Guess I just want to know if not having those connections on my harness plugged into anything will cause it to run funny or any issue like that.

thanasi85 said:

I was going to look for a block from years 91-96

Will I need to worry about the knock sensor and I think the block temp sensor since my wiring harness is set for those and an HO motor doest have those sensors.. Guess I just want to know if not having those connections on my harness plugged into anything will cause it to run funny or any issue like that.

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The knock sensor is not a necessity. The CTS is necessary and can be installed into the HO block, there is a pipe plug in the block near and in front of the motor mount bracket. If the CTS is not connected the RENIX system will stay in "open loop" and run rich like its cold all the time.

I recently installed a 98 long block in my 89MJ and used the RENIX intake. It works great. I decided to move the CTS to the T-stat housing for ease of future diagnostics and replacement. The HO T-stat housing is drilled and tapped to fit a RENIX CTS. You will need to move your CTS wire harness plug up near the power steering pump.

Here is a pic of the relocated CTS

This may also help you.

BTW, the block is drilled and tapped for the knock sensor. You can remove the 5/16" square drive plug from the coolant passage on the later block and put your CTS in the original location if you'd like.

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

Thanks for all the advise. I feel good knowing I can use a HO Block with my Renix head.. gives me a lot more motors to choose from at the auto wrecker.

96 still had the hole in the rear of the.head for the.gauge sensor.as far as I know, all 96 should be the same, as they were still the early style bodies. Later dash and cluster.didnt.come until the 97 year

souske said:

96 still had the hole in the rear of the.head for the.gauge sensor.as far as I know, all 96 should be the same, as they were still the early style bodies. Later dash and cluster.didnt.come until the 97 year

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The engine pictured above is a 98 XJ 4.0 LB and it had the 1/8" NPT hole in the rear of the head for the temp sensor as well. I was surprised when I pulled it. It could have been a older 0630 head on the engine but it sure looked like the original head/block combo.