4.0 swap AC question

zebraic · Jul 25, 2007

This seems like a no brainer, but i just needed confirmation before i went ahead. I started lookin for a 4.0 to swap out my 4.2 and i started wondering what all i needed on the new engine. i have air conditioning in it now and would like to keep it so i can convert to onboard air. My question is do i need get the 4.0 with air conditioning and is that set up compatible to my AC i already have. Or can i get one without and put my AC on it? I assume i can just plug the tubes in to the AC on the new engine and call it good, but i dont want to buy an engine an get pissed later. thanks!!

junkyard jim · Jul 25, 2007

What compressor do you have now? What year Jeep? I put a '93 ZJ 4.0L into my '84 J10 (it needs wiring done before I can run it)

zebraic · Jul 25, 2007

junkyard jim said:
What compressor do you have now? What year Jeep? I put a '93 ZJ 4.0L into my '84 J10 (it needs wiring done before I can run it)

im not sure what i have now. but its an 87'... how hard was the swap with a zj 4.0?

junkyard jim · Jul 26, 2007

HO is easier than Renix to put in (wiring wise) but Renix works better ('87 to 08/90). Are you doing the EFI too? Biggest problem is clearing the brake booster with the EFI intake (I'm swapping a Hydroboost on)

zebraic · Jul 26, 2007

junkyard jim said:
HO is easier than Renix to put in (wiring wise) but Renix works better ('87 to 08/90). Are you doing the EFI too? Biggest problem is clearing the brake booster with the EFI intake (I'm swapping a Hydroboost on)

y does the renix work better for those years? i thought the HO would have been better, but i didnt even know there were two different kinds til like a week ago lol. Wats the difference between them? and yes im doing the efi too. so what did u think about the AC question? can i just find a motor with AC on it and hook up my hoses?

junkyard jim · Jul 26, 2007

Those years ARE the Renix EFI. It has a knock sensor, so if you do a 4.0L head on the 4.2 or even shave the head on the 4.0L it won't ping as much due to the higher compression. The computer automatically retards timing. The EGR valve also helps cut down ping by reducing NOx and lowering combustion temps.
The HO wiring is easier because al that you need is under the hood. If you are going to onboard air, why fill the system and drain it? You can stack the round style AC compressors to have both AC and onboard air if you have room under your hood. (My J10 does but my Comanche doesn't)
The round style 4.2 and 4.0 compressors are compatible (and some are interchangeable) but check out the online AC training to find out the right way to set it up.