How to perform a cylinder head swap on a 4.0

[WVJeep304]

Somehow all of my photolinks got messed up during the copy-paste. I'm working on fixing them now.

A couple years ago, I had to replace my 0331 head due to the infamous crack between cylinders 3 & 4. I had never dug into a Jeep engine very far before, but wasn’t about to pay the shop $800+ in labor for something I had all of the tools to do on my own, and plenty of time to do it since this happened in the midst of covid. I took pictures of this process, however, I can’t find all of them, but I’ve included below the ones I do have.

Note: This is not a complicated job, and not one to be intimidated by. The closest thing to a “specialty” tool required would be a torque wrench and a 12pt socket. That said, know your limitations: If you can’t figure out how to remove the throttle cable or unplug some of the sensors to get things out of the way, you may not want to tackle this job until your skills advance. The following was performed on my 2002 TJ. While the process will be mostly the same on all Jeeps, it can vary due to any modifications you may have under the hood or the different factory configurations throughout the years.



In my situation, I ordered a new head from Odessa/Clearwater Cylinder Heads. I couldn’t be happier with the product I received. The head came assembled with valves/springs and was packaged well. I ordered the plethora of other parts from Quadratec, Summit Racing, and Amazon, as well as picked up some miscellaneous items at Advance Auto Parts.

Required tools:

Basic Socket Set
Torque Wrench
13mm deepwell 12pt socket
Gasket Scraper
Scotchbrite Pad
Screwdriver
Small Prybar
Fuel line disconnect tool
Oil/Coolant drain pan
Your penetrating oil of choice

Optional tools:
Pneumatic or battery powered ratchet
Small impact
Pneumatic or battery die grinder
Empty corndog box







Parts & Materials:

-Headgasket (I went with Felpro)
-Fuel Injector O-rings (may not be necessary for you, but I wanted to replace the originals)
-Water outlet gasket
-Valve cover gasket (I used Felpro)
-Exhaust/Intake manifold gasket
-Head bolt kit (I used ARP)
-Rocker Arm assemblies (if not reusing what you have)
-Pushrods (if not reusing what you have)
-Coolant
-Oil
-Filter
-Assembly lube
-Loctite 592 or equivalent per FSM (I used Permatex #59235)
-Autolite XP985 spark plugs (again, you may be able to skip this part, it was time for me)

**I will not be including torque values in this article due to potential variances from year to year and/or discrepancies between different manuals, etc. I’d recommend referencing the FSM, along with some internet research to find the proper torque values for your situation.**



To start with, disconnect the battery to prevent any unwanted sparks and potential damage. Then, unhook the upper radiator hose, along with the two coolant lines running along the passenger side of the valve cover and let the coolant drain. While this is happening, go ahead and start disconnecting the throttle cable from the throttle body. You need to remove the air intake pipe and unplug all vacuum lines, pcv system, and sensors attached to the intake, throttle body, and head/valve cover. I also removed all of the EVAP equipment attached to the driver side fender to gain more room. It wouldn’t be a bad idea to label what you disconnect and take pictures of everything so you can ensure you put everything back together properly.

At this point, go ahead and remove the belt. Once removed, take the bolts out of the power steering pump and lay it/tie it up out of the way. Remove the idler pully to the left of the water pump.

Now, go ahead and remove the water outlet (thermostat housing) and set it to the side. You should now have an unobstructed view of the intake manifold and valve cover. The order for the next couple of steps isn’t really critical, I would just do them before popping off the valve cover.

Remove the fastener from the clamp that secures the two A/C lines to the head and pull the lines forward out of the way. Then, remove the bracket. Next, disconnect the fuel line at the fuel rail and unplug all of the electrical connectors at the injectors and at the end of the fuel rail if you haven’t already. Once that is done, you can remove the wire harness and cover mounted about the fuel rail and lay it out of the way or strap it to the hood. Then, go ahead and remove the 4 bolts securing the fuel rail. With the bolts out, a firm tug on the fuel rail should pop the injectors out. Some struggle with this, some have no issues, so YMMV. Make sure your injector o-rings are all accounted for and set the fuel rail and injectors off to the side. **A lot of people leave the fuel rail and injectors installed and remove the manifold. I wanted to do a quick R&R on my injectors anyway, so I removed the rail and injectors**

Next up, go ahead and remove the coil pack and the sparkplugs. Look around and see if there’s anything else that seems like it could be in the way of removing the head. For me, I was clear at this point, with the exception of the valve cover, intake, and exhaust manifolds which are up next. If you see anything else that could be in your way, go ahead and remove it.

Now, remove the bolts securing the intake manifold. I believe there are 4 on top. If memory serves me correctly, Now is the where the 2nd most annoying part of this job begins: removing the bolts at the bottom of the intake manifold. Some people drop the y-pipe, some remove the fender, some do both. I did neither. I left the exhaust manifold connected to the y-pipe and just knuckle-busted and cussed my way through it. The bolt below the #3 injector is the most difficult. Do what you have to do to gain access to these bolts with a wrench or socket. I believe there are a total of 11 fasteners securing the intake and exhaust manifolds.

 

[WVJeep304]

With the manifolds out of the way, you can now move on to the valve cover. Remove all fasteners and set the valve cover to the side. Don’t toss it around too much. It takes less force than you think to bend the mating surface out of shape, and these things can have a hard enough time sealing up on their own without your help.

Now, you need to remove your rocker arms. If you know you’ll buy new rocker arms and pushrods, then you don’t need to worry about order. However, if you’re unsure or know you’ll reuse them, this is where your corndog box (or any box I guess…) comes in handy. Poke holes in your box in rows. Label it somehow so that you know they’re in 1-12 or Front to Rear. As you remove the rocker arm assemblies and pushrods, keep them in the same order and matched together as they were installed, and place them in the holes you poked in your box. To remove the Rocker arms, simply remove the bolt you see in the center of the rocker. You’ll be removing bolts/rocker arms 2 at a time. Once you get those pulled out, simply grab the push rods and pull them out and put them in the corresponding holes in your box. Repeat the process until all rocker arms and pushrods have been removed.

 

[WVJeep304]

With that done, you are ready to unbolt the head. Take your 13mm 12pt socket and go around removing all the bolts around the perimeter of the head. The ones against the firewall can be a little tricky, but not awful. These bolts can technically be reused once, for a total of 2 fastening cycles (once from the factory, and once again). I opted for all new bolts because if I’m this deep in, I might as well.

**At this point, check the coolant pipe at the passenger side front of the head. If it is close to the head or otherwise appears to inhibit the ability to remove the head, you should be able to turn it far enough to the left to provide adequate clearance.**

It’s time to get that heavy hunk of junk off of the block. I was by myself at 11pm and didn’t have a shop hoist, so I used 2 bolts, a short piece of rope, and some acrobatics to remove it on my own. I threaded in a bolt on opposite ends of the head—one on passenger side, one on driver, one front, one rear. I then took a piece of rope around 3ft long or so and tied it around each bolt. I then climbed up on the front bumper and managed to use the rope as a handle and lifted the head off of the block, pivoted around, and climbed down to set the head on the floor. If you’re more flexible and have a better back than I do, this may be no big deal for you, but it was a little bit of a challenge for me.

With the old head out of the way, now you need to start cleaning up the mating surface of the block. This is also a good time to take a look at your cylinder walls and tops of your pistons to make sure there’s nothing evident that would keep you from finishing this job (hole in piston, etc.). You can cover the lifter passages and pistons if you like to keep material out. Use a gasket scraper to remove as much of the material as possible from the mating surface. If necessary, use a light scotchbrite pad to help with this. If you have a die grinder, it’s a real time saver here with a roloc disc. Use the least abrasive material you can get by with as to not remove anything other than gunk and old gasket material. Once the heavy stuff is gone, I sprayed a rag with brake clean and wiped down the surface.


I decided at this point to take a break from under the hood and went ahead and soaked my injectors in some Seafoam and cleaned up the intake manifold and throttle body. While the injectors soaked a while, I went ahead and placed the head gasket and prepared to install the new head. I once again threaded bolts into the head and attached my rope handle and used it to hoist the head up to the engine bay. I then **CAREFULLY** lowered the head into position over the alignment dowels on the block and let it sit down onto the gasket. Another set of hands certainly makes this all easier, but when you’re on your own, you do what you’ve gotta do.

 

[WVJeep304]

Now go around and start threading your new head bolts in by hand. For the #11 head bolt (driver side front), you need to coat the threads in Loctite 592 or similar per the FSM, as this bolt goes into a water jacket. I used Permatex #59235. To tighten these bolts, you have to follow a specific torque sequence and order as illustrated below.

This should be done in 3 passes as follows:

1st Pass 22ft lbs
2nd Pass 45ft lbs
3rd Pass 110lbs*

*All bolts except #11 get 110ft lbs. Bolt #11 that goes through the water jacket should only be torqued to 100ft lbs.



Once your head is installed and all torqued down, you can begin installing your pushrods and rocker arms. If you’re using new parts, order doesn’t matter. If you’re reusing the originals, reinstall them back into the same position from which you removed them, which should be easy to do if you used your corndog box to keep them in order. Coat the pushrods in assembly lube as you drop them into place. I also doused the rocker arms with some assembly lube as I installed them for good measure. Look up the torque spec and tighten accordingly. This is another area where I saw conflicting information about torque specs and technique. Therefore, I will not supply a torque spec. I don’t know if it actually varies by year or how much published conflicting information exists, I just know I found a lot of different numbers when I looked online. I ended up choosing a number I was comfortable with and went with it. There’s also debate about whether you need to rotate the engine as you torque these down. If I remember correctly, even the FSM states this isn’t necessary, so I chose not to and it worked perfectly.

Now would be a good time to go ahead and drain the oil. Any contaminates that may have ended up in the oil can be removed before first start up. Once you’ve emptied out the oil pan and replaced the drain plug, I like to put a little oil in each rocker arm. At this point, install the valve cover gasket and reinstall the valve cover, using the proper torque sequence. Go ahead and refill with your favorite oil before you forget.



Next up, go ahead and start working on that exhaust and intake manifold. Remember when I said that removing it was the 2nd most annoying part of the job? Well, you’re about to meet THE most annoying part of the job. I’m not going into extended detail on this, because it’s just all the reverse order you used to remove it. But a tip would be to leave all the bolts loose until you have the exhaust manifold and intake manifold attached and all bolts installed, then go back and tighten. Don’t forget to stick that gasket in there or you’ll be doing it all over again!



Go ahead and reinstall your water outlet/thermostat housing. Everyone has their preference here, but I just use a good Felpro gasket with no rtv or copper spray. Do what you prefer/what works for you. Make sure you install the thermostat in the right direction and orientation. You can now reinstall the idler pully, the bracket that holds the A/C lines, and power steering pump. Everything from here out is literally the reverse of removal and I don’t believe warrants a detailed explanation. Reconnect your coolant lines and fill with coolant, following procedure for burping the system upon startup. Make sure all electrical connections are hooked back to where they came from and all grounds reattached (don’t forget the one on the back of the head!) The same goes for the vacuum lines. Once you have everything reinstalled and reconnected, hook the battery up and give her a crank. It may be a little noisy at first, but should quiet down in seconds. Let it run and get up to temp so you can burp the system and keep an eye out for any issues or check engine codes. That’s pretty much it!

It is recommended to do a couple of short interval oil changes once everything is back together to help remove any residual coolant or gunk that could be left behind. I personally did this by using the cheapest oil I could find and letting the engine run for about 30min, then draining the oil. I refilled and this time ran this oil for 800-1000 miles and then did another oil change. If you're still seeing signs of coolant at this point, repeat the process once more. If it doesn't clear up at that point, you may still have coolant entering your oil and will need to figure out where and why.


This seems like a bit of a daunting task. My descriptions aren’t perfect and may make it seem worse than it really is. But I assure you, the hardest parts are dealing with the bolts for the manifolds and actually lifting the head in and out of the engine bay. If you can have a helper, it will go much smoother. An engine hoist or something similar would be equally beneficial. This job took me around 6 weeks I believe due to waiting for parts to come in thanks to covid delays. I probably only had around 5 hours of actual work involved in the job though, not counting some extra things I took on as I waited for parts. Make yourself a list of items you may want to check or replace while doing this. You gain more access to make some jobs easier so it could keep you from doing something more than once. Keep in mind it’s not recommended to change lifters without changing the cam. Some people do this anyway and have no problems, I’m just passing along what’s recommended.

All in, including the cost of the new cylinder head, I think I had around $1000 in the whole job. The head has gone up quite a bit since I bought mine, so it may cost you more now due to that, but some of the other parts may have been more expensive at that time, so it may be a wash. I apologize for not providing more specific details as to torque values, but with all the conflicting information I ran into and some of the arguments I read, I don’t want to unintentionally provide you with incorrect information that causes you damage or wastes your time and money. Hopefully you don’t have to do this job anytime soon, but If you do, I hope this article helps you out in some way and that your job goes off without a hitch.

If anyone sees anything I missed or anything incorrect, let me know and I'll fix it.

 

[WVJeep304]

Ok...I had some real issues getting the pictures posted. They've posted out of order, some didn't post at all. Some things double posted. Hopefully its legible at this point. I'm going to give my eyes a rest and check again later.

 

[JasterMereel42]

I'm bookmarking this because I have the non-TUPY head and I'll probably have to do this at some point. great pics & great write up.

 

[Mercury]

Fantastic write-up on a job I plan to take on soonish! Thank you!

 

[jeepguy03]

Just saw this thread, excellent write-up! I've replaced 3 of the 0331 heads now, one on my own Jeep I previously owned, and two for friends, and this write-up is a great guide. I used two of the Clearwater heads, and one from Alabama cylinder. Not sure if Alabama cylinder is still in business, but regardless I had no issues from any of them.

One thing I recommend though for anyone doing this, is after you replace the cylinder head do a couple short interval oil changes, like 1000 miles or so. That will help get any residual coolant or junk from the install process out of the engine oil. Even after two changes at 1000 miles there was still some trace amounts of coolant showing up in a Blackstone used oil report. The engine we did the report on had been mixing coolant for a few months though. We did a few more reports later on and they looked much better.

 

[WVJeep304]

Just saw this thread, excellent write-up! I've replaced 3 of the 0331 heads now, one on my own Jeep I previously owned, and two for friends, and this write-up is a great guide. I used two of the Clearwater heads, and one from Alabama cylinder. Not sure if Alabama cylinder is still in business, but regardless I had no issues from any of them.

One thing I recommend though for anyone doing this, is after you replace the cylinder head do a couple short interval oil changes, like 1000 miles or so. That will help get any residual coolant or junk from the install process out of the engine oil. Even after two changes at 1000 miles there was still some trace amounts of coolant showing up in a Blackstone used oil report. The engine we did the report on had been mixing coolant for a few months though. We did a few more reports later on and they looked much better.

Thank you. I had to think back a bit to try not to miss any details, hopefully I got enough included that it helps someone. Good call on the oil change interval. I should have included that, and will go back and add it. I personally didn't see any coolant in my oil, so I assumed it had very trace amounts, but did short interval changes to be on the safe side. I bought a bunch of the cheapest oil I could find, and for the first round, I just put in some fresh oil and ran the engine for 30min and changed the oil again. For the next round, I believe I put somewhere between 800 & 1000 miles on it before changing it again.

 

[Mercury]

Would this be a situation where you'd want to run higher zinc oil or an additive while it breaks in?

 

[WVJeep304]

Would this be a situation where you'd want to run higher zinc oil or an additive while it breaks in?

I wouldn't think it would matter. After the initial junk oil changes to flush everything out, I went back to the conventional Pennzoil I was using before. I ran it up until my last oil change where I switched to Rotella conventional.

I only switched in part to see if I noticed any difference, and also due to it getting harder to find Pennzoil conventional in my area. I've had zero issues since the head swap (no issues related to the head swap anyway.. Evap codes are another story).

 

[jeepguy03]

Would this be a situation where you'd want to run higher zinc oil or an additive while it breaks in?

Nah. Zinc is only really needed for the flat tappet camshaft, and since the valve train was all re-used, nothing really needs to break in. With that said, the 4.0L has pretty low valve spring pressures (with the stock cam) so high zinc oils aren't needed besides breaking in a new engine/camshaft. The only reason you would need to run it is if you had a stroker with an aggressive cam. I've done a few used oil analysis over the years with my different Jeeps, and regular old Valvoline and Pennzoil showed the lowest wear numbers. Use decent oil and change it regularly and you will be good to go.

 

[Mercury]

Nah. Zinc is only really needed for the flat tappet camshaft, and since the valve train was all re-used, nothing really needs to break in. With that said, the 4.0L has pretty low valve spring pressures (with the stock cam) so high zinc oils aren't needed besides breaking in a new engine/camshaft. The only reason you would need to run it is if you had a stroker with an aggressive cam. I've done a few used oil analysis over the years with my different Jeeps, and regular old Valvoline and Pennzoil showed the lowest wear numbers. Use decent oil and change it regularly and you will be good to go.

That makes sense. I'm trying to gather this information now, well before I actually tackle this. Still need to find a good brand.