As per this write up http://monsterslayer.com/jeep/40Head/40Head.htm

It states that a 4.0 head when put on a 258 often needs to have the intake/exhust side 'extra' water jackets sealed.

Well I am doing this swap (and adding FI) and just put the 4.0 head on for a test fit. I then took a marker and traced the block onto the head where it over hangs (inbetween cylenders) and the water jackets do not over hang, they remain on the top of hte block surface.

I have read that as long as they do that its okay to run it w/o sealing them off.

I partly want to seal them just to be sure, but money is a big issue right now and the extra $50-100 it would take to get that done could be used else where (ie car payments)

By my numers I have a solid 1/16th" + of space between the edge of the block and the edge of hte water jacket. Do you think that is enough mating surface?

Anyway I am looking for some input, what would you do, weld it or just let it seal up because it mates up to the block.

Its a 1990 YJ with a reman'd jasper (30k) the head is off a 91 XJ with 130k

Dan

Later 258 blocks (89?+) are wider than the earlier blocks and don't require blocking the water jackets.

For just a few bucks you can use epoxy in the holes for the extra insurance.

I would think the head gasket would be able to seal it when equally torqued - even though there will be less sealing pressure on the holes that aren't supposed to be there depending on which type of head gasket you use. However if for some reason its not adequate - do you really wanna have to pull the head off again to plug it up? Weld it up yourself (if you are a good welder), and have a good machine shop re-grind the surface of the head. It really shouldnt cost that much extra either. When I rebuilt my brother's 22r the machine shop had to do the same thing with the aluminum head since the coolant corroded it to the point where it was getting too close to the combustion chambers. I would think cast-iron is a bit more forgiving.

For just a few bucks you can use epoxy in the holes for the extra insurance.

What he said ... !

another vote for some epoxy, or even JB Weld in the ones you're closing off.

I have done 3 of them,I put the head in a milling machine,and with a 3/4 inch endmill,drilled the holes to 3/4 inch,got 12, 3/4 inch, deep well freeze plugs,mixed up some marine tex,coated the freeze plugs with it,and install them in the head.

Anybody got a walkthrough written up on this? I've got a 4.0head, 4.2 block, xj wiring harness and xputer sitting in the garage getting ready to start assembling.
j2076

Anybody got a walkthrough written up on this? I've got a 4.0head, 4.2 block, xj wiring harness and xputer sitting in the garage getting ready to start assembling.
j2076

Look at the very first sentence, click the link that says "Monsterslayer".
Jeez, you didn't even have to touch the search button.

Got info on the head swap Dougy.....Looking to learn more about setting up the harness or did you miss that in my post...........

I used JB Weld on mine and has been holding up for almost 2 years now. I read a lot of different writeups and ended up getting some water soluble packing peanuts and put them in the jacket holes then a few globs of JB weld that we made sure was smooth. Gave it over 24 hrs before putting back on and it's been good to go. We even ran the water through ourselves (bypassing the radiator) to make sure chunks of packing peanuts wouldn't get stuck in the radiator, and we didn't even see any chunks at all.

Well I dropped it off to get decked (head has 140k on it) and was talking to the engine builder. He has a 258 he is building and said he had never heard of someone else doing the swap, but that he was plannin on doing it himself to his CJ.

Im goin in on monday. I told him I would like to expoxy it at the very least and he said he had some stuff that would work, its for engine internals or something. He used to build the engines for sprint cars and said he used it in alot of other engines.

J2076

I too am using an XJ harness and computer. I have searched high and low and not found a write up on it. good luck

I used quiksteel.

Just to be on the safe side. spray both sides of the headgasket with copper coat before assembly.

Got info on the head swap Dougy.....Looking to learn more about setting up the harness or did you miss that in my post...........

Yep, I missed the harness part, selective reading.
Start here and you'll find some info about a data base being set-up.
Try here (http://www.cjoffroad.com/forums/topic.asp?TOPIC_ID=1097)

How many people have welded it themselves before having it decked?
Is mig an acceptable method? I wouldn't think that the head rebuilders are tig'ing it. :confused:
Does it need to be preheated or anything?

How many people have welded it themselves before having it decked?
Is mig an acceptable method? I wouldn't think that the head rebuilders are tig'ing it. :confused:
Does it need to be preheated or anything?

The process is called fuse-welded. I don't know the procedure. I don't see why you couldn't just bore the hole round, push in a plug and TIG it around the perimeter. You'd still want to resurface though.

Umm, I won't be tigging anything. :D No tig equipment or skills. :(
I was wondering if I could mig it though. I have a Millermatic 175 and a rosebud if it needs to be preheated since it's cast.
What is the rebuilder's process for this fuse-welding?

Here's a writeup I did 5 yrs ago with the 4.2L block/4.0L head/MPI lashup.

From: Jeff Reynolds
Subject: Report: installing a 4.0L head on a 258 block.
Subject: RE: [JP] Clifford 272 EFI cam for 258 with 4.0 head
Date: Thu, 14 Oct 1999 07:22:54 -0800

[Dave wrote:
Your cam [Hesco 264-14] sounds like a carbon copy of a Clifford 264H cam. Did you CC your
heads by any chance? Or done a compression test? I'm curious to see what
your compression figures are.

On another note, I'd bet that the Mopar 4.0 head gasket is thicker than
the Fel Pro. At least that's what Jason Weir tells me... Tell me about
your head swap! Did you seal the water ports, or let the gasket do it for
you? What year is your 258 block?

My current cam has considerably more lift than many of the Mopar
performance cams. Pro-Tech says to keep the present cam, Clifford says to
chuck it and install the 272 EFI if I have 9.5 to one compression. To say
the least I'm a bit mystified by all of this. Everyone I ask has a
different way of looking at it. I'd love to save money and stick with what
I have, but I don't want any more detonation problems! If I need a cam, so
be it! I'm gonna have the head off any way.

Dave Arieno]

<SNIP>

(jefe writes):
Dave,
Here's a little report on the 4.2L to 4.0L head swap. This info took a lot of digging to assemble, so be sure to save to file.
I had to take my rebuilt, stock '82 4.2L head off a few months ago to find out why I was using so much oil. Rings were leaking a bit, and the valve guide seals were shot. I have had the MPI installed for about 20K miles, and as the oil consumption increased, so did the need for higher and higher octane gas. I decided to go all the way and install the 4.0L head. I obtained a rebuilt '95 XJ head, all new parts and a 3 way valve job for about $400. Valves are larger, much larger than the 4.2L head, and the 'breatability' of the head's intake and exhaust passagways is outstanding.
The MPI bolts right on the new head, albiet a little higher on the head. I had the Borla header for the 4.2L which now didn't fit, (no 4.2L exhaust manifold fits the 4.0L head, so don't even try) so I picked up a used and rebuilt '94 stainless exhaust manifold for $140. It looks like a mini Borla, and is successfully weldable, unlike the cast iron manifolds. I had a look at the earlier 4.0L exhaust manifold (used on the '88-90, Renix 177 hp, 4.0L's) and can see why they have less H.P. It's a cheap and ill engineered manifold. Don't waste your time with it. I also found a used 4.0L aluminum valve cover and cleaned it up.
You must fill the (12) triangular water jacket holes along the edge of the head with epoxy. The reason you must plug the holes at all is because that part of the head is very close to the side of the block and might blow out if not plugged. The head gasket hangs there too. Some have even lived dangerously and just not plugged the holes. Some have reported that Hesco and Clifford weld these shut. I talked to the powers to be at both shops and they said they do not weld them, and never have. They use a very hard 2 part epoxy. Hesco recommended an epoxy called, "Metalax", a bondo type hi-temp epoxy. This is totally unavailable in So. Cal. Clifford recommended, "Manley", a filler-bonder, which I could not find anywhere either. Mike Brink (who did this same swap a couple months before) used a product called, "Marine-Tex, Gray" 2-part epoxy. I finally found it a large boating-marine supply place. This is what I used. There are other epoxies available in auto parts stores, but none of them looked as good as the Marine-Tex which is extremely hard, chemical proof, and heat resistant.
The (12) holes in the head are kind of like eliptical triangles. The narrowest part is right at the head surface, and it gets wider as you go into the head, making it a problem of enough pressure to make the plugs stick. Some have suggested using a fine cloth mesh-like screening and pressing the epoxy down in, like a bag, and cutting the excess off after curing. I didn't like the sound of that because the epoxy would have a hard time sticking to the walls of the head, so I used Hesco's trick using (now don't laugh!) styrofoam peanuts squeezed like ear plugs and pressed into the holes and expanding forming a dam for the liquid state 2 part epoxy to settle into. It needs to be at least a quarter inch thick. Bennie at Hesco said the foam just disolves and becomes part of the coolant after curing. It works fine.
My '82 block, which was still in the engine bay, has 7/16th" threaded holes for the headbolts. Ididn't want to pull it again and decided to use the 7/16" bolts. Clifford assembles and sells new head bolts for this arrangement and also has pairs (that's really all you need) of tempered sleeves to use in the 1/2" holes of the head. Using a sleeve at either end of the head insures an accurate mating of the head/head gasket/block. Clifford said if you are real carefull, you don't even need the sleeves. Everyone recommends using new headbolts for this swap.
Now, listen up. The headbolts you use should be torqued down to the specs that accompany the headbolts. The torque specs have all to do with the bolts and not the two surfaces that you are mating. For the life of me I could not find new 7/16" headbolts (the 4.2L bolts) for my project, so I reused the same ones again. It seems fine after several thousand miles of operation. The later CJ's and all YJ's use 1.2" bolts. If you have 1/2" threaded holes in your block, all the holes line up with no redrilling. Just use a set of new 4.0L headbolts and torque them down as per the 4.0L head install, which gets most of the bolts @ 110 or 115 ft. lbs. These, I am told, are made to stretch, unlike the 4.2L bolts which aren't. My 7/16" bolts were torqued to the 85 ft. lbs. per the 4.2L specs. (Headbolts: $60 from Clifford Performance; I've heard less than $20 from Mopar Performance)
Some folks that have done this swap complained of the power steering bracket having to be refashioned in order to fit around the front cyl. exh. tube on the manifold. I did not have to do any of this. It depends on if you have A.C./ and/or air pump, (which went away during my MPI install) and which year engine/bracketry you have, and which version of the serpentine belt you have.
I had to have a OXY sensor bung welded into my new exhaust pipe just after the stock 4.0L manifold (which doesn't come with a bung). It doesn't matter where it goes, as long as the wire will reach the sensor from the loom. Mine is about 12" downstream of the end of the exhaust manifold. I figured it would burn out more slowly if it was farther away from the heat source.
After finding the right epoxy it was just a matter of putting it back together. I'm very happy with this setup and it should pass smog with flying colors as the aftermarket MPI is legal here in CA. and way cleaner that the old BBD days.
I will eventually do a dyno readout of this set up, but, seat of the pants, it feels like about 25 more H.P. , and has noticably more torque in all ranges, compared to the previous stock head/ 4.4Lblock/MPI arrangement. I am using regular gas again (as Mike Brink also reports), and even though the compression, on paper, is higher, the head design allows a lower octane requirement before detonation (ping).
[This was 5 yrs ago and the engine works fine and has no woes with the plugs. I like the engine set up alot, although I would probably go back to a SBC if I were to do it again.]
regards, as always, jefe

A while back, HESCO stated they "furnace welded" the ports on their 4.0 conversion heads.
Whatever that means. :confused:
I couldn't tell there had ever been any holes in the head they sent me in 1998.
Looked like solid weld steel ... no color difference nor triangle boarders showing. Maybe it's still a trade secret?
Mine was P & P'd by hand then ... later on they were offering CNC chamber milled units.
I still think HESCO is the best in the Jeep I-6 business.
They know thier chit!

A while back, HESCO stated they "furnace welded" the ports on their 4.0 conversion heads.
Whatever that means. :confused:
I couldn't tell there had ever been any holes in the head they sent me in 1998.
Looked like solid weld steel ... no color difference nor triangle boarders showing. Maybe it's still a trade secret?
Mine was P & P'd by hand then ... later on they were offering CNC chamber milled units.
I still think HESCO is the best in the Jeep I-6 business.
They know thier chit!

No joke there, Bennie's the man with the plan. He's helped me many times with some of the smallest irratating quirks my MPI was going through. Those heads are big $ though. They did offer to exchange my small injectors for the large ones for an awesome price. Big props to HESCO.

Well I had them welded and the head decked and it cost me a hole lot of nothing.

The guy was in need of a 258 head/intake/valve cover for his CJ, so i gave him mine that came off my my 258 (30k onthem) and he called it even.

So parts that would have sat around collecting dust got my head work done for me.

I have it together, now im working on wireing it all up. its probing to be a PITA already

Dan

damn I wish I found a guy running a shop in need of stock 4.2L shit... how are you doing your FI? just take the shit off a stock 4.0? let me know how the install is; i'm about to start searching for info on it

damn I wish I found a guy running a shop in need of stock 4.2L shit... how are you doing your FI? just take the shit off a stock 4.0? let me know how the install is; i'm about to start searching for info on it

Well I hit quite the wall, having two computers is hard work. and i am totally confused over it.

I have power to my coil but no spark out of the coil.

stupid computer systems

That's why I stick with a carb.