4.0 manifolds on a 258 head?

[LorenWalding]

I am new here, so this may have been asked, but I could not find it. Will the intake and exhaust manifolds off a 4.0 fit onto a 258 head? Or will I need to swap the head over and modify it to fit? I currently have a 2.5 in my yj , but was given a 4.2 so I have nothing in it yet, but I am trying to keep the cost down as much as possible for an EFI swap. Thanks, Loren

[eliv1]

I will fit, but with some mod's into it, like cutting of the bolts ears, grinding in some places to clear the exhaust header.
you should also port match the intake to the head.

good luck!

[LorenWalding]

Thanks for the info, I am still not sure which way I'll go. Iam just wanting to check my options.

[stroked'73]

The exhaust ports are round on the 4.0 - square (rectangular really) on the 258. I think even though it'll cost a bit more you'll be way better off swapping the 4.0 head. You'll end up with more power, and all the manifolds will bolt up like they should. Especially since you want to do FI. If you can't find/afford a complete head right now, just run the 258 carbed as is until you can get all the pieces together for you FI swap.
With so many people trying to get an HO head, you could probably pick up a renix head for next to nothing - most folks think they're junk but the difference between them isn't as much as you'd think. Plus the renix system is fairly simple. You could probably even put an HO manifold onto the renix head if you wanted to run MPI system instead.

[5-90]

The later 258 heads also have siamesed exhaust ports for #3 and #4 cylinder - the 242 heads do not. You'll have to separate those two ports using something high-temp (JB-weld?) and match it to the exhaust - then match the exhaust manifold entries to the exhaust ports in the head (rect. to round...)

Short form - it's going to be a fair bit of work. I'd not want to try it - just swap the head, pick up a few points of compression and fuel injection, and you'll be happier.

[eliv1]

there's no doubt that an HO head will give the most beneficial performance's, but a 258 head will work just fine.
you could install it on the 258 head, and then later, find another 4.0L manifold, their very common, you could maybe put
a 99+ intake when you upgrade to a 4.0L HO head too.

[IH 392]

The later 258 heads also have siamesed exhaust ports for #3 and #4 cylinder

All of the 199, 232 and 258 heads have a "common" exhaust port on #'s 3&4, as far as I've ever seen.

[salgofnir]

I recently inherited an 81 CJ-8 with 51K original miles. I would like to do a head swap and MPI. What would be a good year to just pull it all as one unit (head, MPI together?)

[eliv1]

you could pull the head&MPI from a 91-95 YJ,XJ, or a ZJ(with a 4.0L), allthough the ZJ harness has the most unused wires, and need's alot of thinning to the harness, also the ZJ's had anti-theft, which makes their PCM's unusable.

you could dig alot of info in this forum:

http://cjoffroad.com/forums/forum.asp?FORUM_ID=24

[salgofnir]

What's the deal with the 99+ intake? On Ebay there there is a company J&C that sells remaned 7120s for 260.00. Would this be the best with a 99+ intake.

Just trying to get it right the first time.

[salgofnir]

OK, I figured out the 99+ intake question. If I pull this intake, fuel rail and injectors, will it all work on an OBD I wire harness and ECM?

Sorry if it appears I hijacked this thread. Did not mean to.

[ilber]

I believe 7120 consider to be a better casting, good flowing, has the temperature sensor whole.
As far as the price, not sure. The *core* can be had for waaaay less.
As far as 99+ intake I believe the volume of the runners is greater/flows better. But if you are older XJ there is interference with PS pump bracket thing AFAIK, but better XJ folks chime in here.
I personally don't like buying things like head from an ebay, even if you get legit warrantee. God forbid you need to redeem it.... sending the hunk of steel, time, waiting on the vendor to respond, vs take the head and bring it with me to my local machinist and hold his feet to the fire should the crap happens... just a thought on a flip side my local NAPA wanted like $500 for reman 7120 (and additional like 200 for the core), while pick-n-pull wanted for valve cover-to-oil pan engine 250+tax+tax
Hope I clarify a few things.
Ilber

[salgofnir]

I called around today and found out some disturbing news. First, I found a 95 XJ. The price for the head, intake, wire harness, ECM, distributor was going to be 100-120 if I pulled it myself. The only catch was since the car was a "green" motor (i.e. cash for clunkers) they are not allowed to part out any of the motor parts by federal law. I did not know they were not allowed to part out the motor of a cash for clunkers vehicle.

[ilber]

I thought the accessories can be yanked ( i did for tb and FPR).... 120 sounds fair, at least to me.... don't get me started on the clunker crap...I just migh have an urge to punch a puppy....

[salgofnir]

Have been reading a little this evening. It seems that since I have an 81 with the 7/16 head bolts, I should torque to the 4.2 specs and not the 4.0. Is this correct. I also saw where you torque the outer 4 to 4.2 specs and the inners to the 4.0 specs. Which is recommended here.