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4.0L Head Conversion for the 258

Recently I've been reading about the 4.0L head conversion for the 4.2L

258 Jeep Engines. I have a 1990 Wrangler with the 4.2L 258 engine that needs to be rebuilt. While having this done I was thinking of doing the 4.0L head conversion and was wondering if anyone had any good feed back for the conversion or negative feedback. I understand it can give me more horsepower and better gas mileage as well.

After looking into it it seems that the casting numbers for the 4.0L heads that I should look for are either the 7120 or the 0630 because of flow rates or something. As you can tell I've read some but am not very good at this stuff so was hoping for feedback again.

Thanks.

Reply to
NewbieJeepGuy
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If you are going to be rebuilding anyway, I suggest finding a complete

4.0 and putting your 4.2 crank and rods in it for a 4.6 stroker.

NewbieJeepGuy wrote:

Reply to
jeff

I've checked into that a bit, but not sure I want to go all the far as of yet. Does anyone else have any thoughts on my conversion and whether the casting numbers on the 4.0L head of 7120 or 0630 are the best to go with?

If I change engines completely I've thought of going to the '97 5.2L tsi engine because I was told that would bolt right in as well.

Thanks.

Reply to
NewbieJeepGuy

I have read in the past about using 4.0 head on a 258 and it is not a bad idea. A quick search to refresh my memory revealed a article over in Geocities of such a conversion complete with pic's! It will give you more HP than stock head and more torque than a 4.0 because of increase displacement even if you do not stock it more. Again I would say I think is is a very worthwhile mod.

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TheSnoMan.com

Reply to
SnoMan

The 4.0 head doesn't fit the 4.2 block, it overhangs so you have to block a bunch of coolant holes in the 4.0 head with glue and pray the glue doesn't fail when you are 25 miles from the nearest phone.

Not for me thanks...

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08
Reply to
Mike Romain

This is a public service announcement.

Archived examples of SnoMan's post below. Please take the time read these. They just may save you time, money, and your life in the future. ___________________________________________________________ SBJ: 4T65E

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(Confuses a 4T65e with a 4L65e and won't admit it.)___________________________________________________________SBJ: Dumb brake question
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(Discribes the wrong brakes and won't admit it.)___________________________________________________________SBJ: Front wheel bearings-2000 Blazer??
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(Claims torque specs are wrong when they are not.)___________________________________________________________SBJ: Snoball Defense System v1.01
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(Snoball breaks these out when he knows he's wrong and doesn't want to admit it.)___________________________________________________________

Reply to
Heatwave

This guy does not care if you find a answer or to even help you as he is driven by his own insecurity to lash out at others that refuse to bow to his inmaturity. He is digging his own newsgroup grave not mine.

----------------- TheSnoMan.com

Reply to
SnoMan

Reply to
L.W. (Bill) Hughes III

In article , snipped-for-privacy@snoman.com beats out...

These links contain stuff that 'you' wrote. If you don't like seeing your own post then you could stop posting. BTW I thoroughly enjoy seeing your temper tantrums. ___________________________________________________________ SBJ: 4T65E

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(Confuses a 4T65e with a 4L65e and won't admit it.)___________________________________________________________SBJ: Dumb brake question
formatting link
(Discribes the wrong brakes and won't admit it.)___________________________________________________________SBJ: Front wheel bearings-2000 Blazer??
formatting link
(Claims torque specs are wrong when they are not.)___________________________________________________________SBJ: Snoball Defense System v1.01
formatting link
(Snoball breaks these out when he knows he's wrong and doesn't want to admit it.)___________________________________________________________

Reply to
Heatwave

This really isn't a good place to be getting information for this conversion or much of anything else anymore. It is sad to see what this newsgroup has devolved into. A couple of websites, jeepforum.com or better yet, cjoffroad.com come to mind as much better places to look. Search through the older posts before starting a new thread. The regulars will appreciate that you made the effort instead of wading in and asking about something that has already been covered. You will find the answers you are looking for instead of being dismissed as, "Bah, humbug. Ain't no good". From what I remember, the 7120 was one of the better heads for flow. Yes, the core holes in the water jacket do need attention but are easily remedied. They aren't a big deal. You may even want to check out the strokers group on Yahoo.

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There are lots of good info and helpful people there with practical experience.

"NewbieJeepGuy" wrote in message news: snipped-for-privacy@i13g2000prf.googlegroups.com...

Reply to
J White

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