Head Swap - Pirate4x4.Com : 4x4 and Off-Road Forum
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Old 03-31-2012, 04:31 PM   #1 (permalink)
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Head Swap

Crawled up from the YJ gang to ask a question for a club member.

Don`t know the whole story as an 89 YJ would have a 4.2 so it is a bit difficult to figure out just what he has.

Will/can a HO head fit on a pre-90 block?
What are the issues?

I think I have an 89 4.0 engine non HO. Obviously that will not do. So. I need to find this out.

Because I thought 4.0`s came in XJ`s prior to YJ`s.

Clear as mud ??
Sent with smoke signal.
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Old 04-02-2012, 09:41 AM   #2 (permalink)
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Yes, a 4.0 HO head will fit on a 258 block with some mods. Search the web as it is one of the most common swaps out there. 87-90 XJs had a 4.0 if they were a 6 cyl, non HO and used a renix fuel injection system. The YJs keep the 258 carbed motor up to 90. 91 was the first year for the 4.0 HO obd1 injected motor in a YJ and a XJ. Quick easy way to tell 258s and 4.0s apart is the fuel pump. If it has a mechanical pump, or a place to mount one it is a 258. No 258s were fuel injected from the factory and all had a mechanical pump. 4.0s were injected and have a electric pump. A quick look at the throttle body will tell a renix from a obd1 and later. Renix's have 3 mounting bolts to the manifold and obd1 and later have 4 bolts.
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Old 04-02-2012, 02:47 PM   #3 (permalink)
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try this;

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