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Unread 09-10-2009, 01:43 PM   #1
cgracing
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4.0l vs. 4.0l HO

Is there a difference between the 4.0l and the 4.0l HO? If there is a difference what is it and how do you identify it from serial numbers casting?

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Unread 09-10-2009, 01:59 PM   #2
Louie4
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The only differences I've seen is the wiring but I'm sure there's more to it.
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Unread 09-10-2009, 02:06 PM   #3
sprowley
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There's a fair bit of difference actually.

But first, no YJ has a non-HO 4.0L engine, really only Cherokees from 87-90

the non-HO has a different head and different fuel injection system often referred to as the Renix system. The head is a bit more restrictive and the injection wasn't multiport. After Chrysler bought AMC in 88 they redid the 4.0, gave it the PowerTech HO (High Output) designation and slapped it in Wranglers in place of the carbureted 4.2Ls.

There's a difference of like 15 or 20 ft-lbs and hp between the two versions.
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Unread 09-11-2009, 02:31 AM   #4
cgracing
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OK, I checked it out yesterday. Visually it looks the same with the exception of a/c and a few other minor things. Stamped on the side of the block is I05MXI4 which if I translated correctly would mean-
  • "I" is really a 1 meaning 1991
  • "05" means it was built in May
  • "MX is 4.0L
  • "I4" is really 14 meaning built on the 14th day of the month


Am I correct? If so, this should be a direct bolt in with the same spec cam and injectors as my 1991 YJ 4.0L

Also, There is an automatic transmission included with the sale. Which autos came in these Cherokees?
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Unread 09-11-2009, 08:24 AM   #5
sprowley
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Someone correct me if I'm wrong but any 4.0L from a Wrangler should/will directly bolt into another Wrangler with no differences.

And 91 is when the HO version started so yeah it should be the same specs as any other wrangler 4.0L
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Unread 09-11-2009, 01:37 PM   #6
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I thought I specified earlier, but I didn't. This motor came from a cherokee, the year is unknown.
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Unread 09-11-2009, 01:41 PM   #7
sprowley
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Quote:
Originally Posted by cgracing View Post
I thought I specified earlier, but I didn't. This motor came from a cherokee, the year is unknown.
Oh, well in any case it will bolt up the same. 4.2 and 4.0 of any stripe I think bolt in the same. And as long as you have a complete engine with the harness and computer and stuff... it should just work.
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Unread 09-12-2009, 05:40 AM   #8
cgracing
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Thanks for the help! The noob appreciates it.
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Unread 09-12-2009, 12:24 PM   #9
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Quote:
Originally Posted by sprowley View Post
There's a fair bit of difference actually.

But first, no YJ has a non-HO 4.0L engine, really only Cherokees from 87-90

the non-HO has a different head and different fuel injection system often referred to as the Renix system. The head is a bit more restrictive and the injection wasn't multiport. After Chrysler bought AMC in 88 they redid the 4.0, gave it the PowerTech HO (High Output) designation and slapped it in Wranglers in place of the carbureted 4.2Ls.

There's a difference of like 15 or 20 ft-lbs and hp between the two versions.

Actually the renix injected 4.0's are a MPFI setup FWIW
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Unread 09-12-2009, 12:41 PM   #10
sprowley
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Quote:
Originally Posted by Krochus View Post
Actually the renix injected 4.0's are a MPFI setup FWIW
My bad, sorry! I thought it wasn't. I got the rest right though, yes? I wasn't quite sure about the years but I didn't think the 86 Cherokees had it as an option. Comanches had the Renix 4.0L too, I think.
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Unread 09-12-2009, 04:50 PM   #11
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Quote:
Originally Posted by sprowley View Post
My bad, sorry! I thought it wasn't. I got the rest right though, yes? I wasn't quite sure about the years but I didn't think the 86 Cherokees had it as an option. Comanches had the Renix 4.0L too, I think.


Honestly I only commented on the part I knew. But I need to find out what the mechanical diffrences are as I'm holding onto a couple good running remix 4.0's on the assumption that the long block can be used as a spare for the rigs in my signature.
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Unread 09-12-2009, 05:08 PM   #12
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Any 4.0 from a Cherokee from 91-99 will be a direct bolt in for your 92 YJ. The 4.0's were the same. I only say to 99 because in the 00-01 years, the intake and the ignition was redesigned to a distributor less ignition and the intake was made differently for a better flow. The AX-15 you have was also put behind these from 91-01. So it should be a direct swap.
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