Another 4.0 swap

[9.3x62]

Yo, amigos. The 258 in my 80 Cherk is going down the drain fast. Mucho blowby, and now I think it sucked a valve or something. I wouldn't mind stabbing another 258 into it, but I run into a lot more 4.0 liters out there, so I may very well do that one. My question is, which model of jeep am I looking for? The 4.0 came in several rigs, but as I understand there's things to watch out for between models. I just want to know, which is the easiest model to swap from? I hear things about certain versions with waterpumps that don't fit into an SJ, and I'm aware of the brake booster clearance issue, in which case I may install a late model rounded,intake onto whatever version 4.0 I choose. I guess I just want to know, what's the absolute easiest route to go for swapping a 4.0 into an SJ with a t176 4 speed? I'm searched old forums on the net, but just want a final word. Thank you very much in advance.

[Srdayflyer]

ive got both blocks 258/4.0 in my shop and their identical hole for hole as i wanted to put the 4.0 in my cj , which i have as yet to do as the original in my 75 cj is a 232/3.8 and the damn thing just wont die, ive rebuilt 258/4.2 short block ,the only thing i did to the 3.8 was swap the head to the closed chambered design and a blog with pictures was done here as someone wanted to increase compression inexpensively, the squish chamber is 1/2 of the open chamber design anyway i dont see any issues should you want to go that route, and what you refer to are the early 4.0 block years but over all i'd stick to the 4.2 there was a tv show that did a 4.2 build and they got 1hp per c.i and that was i believe was in a cj7 but the jeep sixes are rated as one of the best ever 6cyls ever built with 7 main bearings, my first cj i got over 300k before the cam wore out, but enough about my experiences, good luck on your choice

[9.3x62]

I would like to rebuild the 258 with a 4.0 head and other goodies, but it ain't at this time in the financial cards. But there are several serviceable secondhand 4.0 liters in my area for cheap. Figured I might stab one of them in and do a nice 258 rebuild later. But I agree, I like the 258 reputation.

[tgreese]

This topic has been covered a lot, here and at IFSJA. Search will provide dozens of threads to read through.

https://www.bing.com/search?q=site%3Afs ... 0+258+swap
https://www.bing.com/search?q=site%3Aif ... 0+258+swap

There is also a sub-forum at jeepstrokers.com called swapology: https://www.jeepstrokers.com/forum/view ... 8b7c96e62d Not a lot of recent action, but plenty to look through. There is plenty of reference material re the 4.0L on that site.

JMO - doing your homework is part of the sweat equity that goes into these swaps. You're asking for the "final word" on swapping an engine that has been gone from production for nearly twenty years into a 44 year old car... kinda think that the word is out and the latest hasn't changed for decades. I've expressed my thoughts on 4.0L and 258 performance in previous threads, and nothing has changed IMO. Stroke ratio, compression, MPI. I'd think a Wrangler would be the best donor, since these are the newest 4.0Ls and the fan should be centered. Unfortunately I've forgotten most of what I've read about this. There are threads on jeepstrokers that discuss the differences in fan offset and block configuration (ie mount changes, like in the ZJ and WJ). That would be a good place for you to start.

[9.3x62]

Yeah, ok. Gimme the dunce hat...

[9.3x62]

Thanks for the links

[tgreese]

Yeah, ok. Gimme the dunce hat...

Not meant that way. No offense, I hope.

[9.3x62]

No offense taken. I was asking a very broad, tired question.

[Anvil-3]

If you’re going to the 4.0 HO the only ones I know you want to stay away from are the 0331 head engines (‘99-‘01 I think) curious to see how this works out for you! Probably most cost efficient than a LS


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[9.3x62]

Right, crummy castings on the late models, I hear. Too bad.

[tgreese]

I recall only the earlier examples of the 0331 head would crack. Both the later heads and the replacement heads are ok, again IIRC. This is covered somewhere on the JeepStrokers site, likely in the FAQs. You can buy a new replacement head for ca $500; thus a cracked head may not be a problem if the donor is cheap enough.

I think avoiding the oddball examples from the ZJ and WJ is more of a concern. They won't match the 258 mounts, again IIRC. Check the FAQs at JeepStrokers.com