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WillyC24 01-03-2011 11:57 PM

4.0 Head Swap on 4.2L 258
Does anyone have experience/wisdom to share on this particular product?

It's the Alabama Cylinder 4.0 head which can be put on the 4.2L. I've read some articles with conflicting advice on whether to use a junkyard head, Clearwater, or Hesco; in addition to specific model years where there are concerns about the heads cracking.

Also, is this a good price? Many thanks.

WillyC24 01-04-2011 10:13 AM

As a follow-up, from all the reading I've done about the 4.0L head swap, the only actual product that I can find on the internet is the Alabama Cylinder link above. (Well, there's the Hesco aluminum head, too)

VaCJ79 01-04-2011 11:25 AM

I got mine from clearwater, 7120 out of a 94, they sell through ebay.

foggybottombob 01-04-2011 11:28 AM

I got one from clearwater also but I will say that I could not tell any difference in seat of the pants power difference. I got a very noticeable power increase from putting in the HEI distributor.

swatson454 01-04-2011 05:35 PM

So what header options does one have when using a 4.0 engine in a CJ? Any long-tube, single-out options?


*Edit* And what are the stock valve sizes of said 4.0 7120 head?

johnson30 01-17-2011 10:22 AM

Hesco sells a 4.0 with the water jackets sealed, gives you a 4.0 valve cover, and the gasket for $1100. Pricey, yes, but I didnt want to seal water jacket ports. And I got a pretty sweet looking aluminum valve cover with it (included).

So, depends on if you want the bolt-on product delivered to your door (like me), or you want to do the work yourself.

WillyC24 01-21-2011 11:40 AM

Can I ask where you found that price? The 4.0 head I've seen on Hesco's website is $1,999. Yikes....

Ben_88Jeep 01-21-2011 11:48 AM

I did the 4.0 head swap from a junkyard in my 88 YJ and noticed a really good power gain in the low end. The only downside to going junk yard is that you will have to machine the head and fill in the ports. When you factor in the cost of the head and the machine shop work, you are almost better off to get one that's already done.

mcmud 01-21-2011 01:12 PM


Originally Posted by swatson454 (Post 10728573)
..... what are the stock valve sizes of said 4.0 7120 head?

While I can't exactly answer the question to that particular head, the "Mopar Performance Parts Jeep Engines" build manual list the 4.0 intake valve head diameter as being 1.782-1.792" and the exhaust as 1.401-1.411"

In speaking with Ron McGinnis @ Alabama Cylinder Head, I'll offer this. He tells me that they cast (iron), mill and installs all new parts while using the #0331 head pattern. That intake valve head diameter is 1.90" and the exhaust head is 1.49".

Alabama Cylinder Head is affiliated (in house) with "Patriot Performance" If the head is walked across the hall then that modification process includes a five angle hardened seat insert installed, its bowl blended and the runners are "cleaned", Patriot Gold springs are installed.

Ron can be reached @2564426773

I want to point out that the modification to the water jacket holes is not performed.

swatson454 01-21-2011 02:22 PM

Great info, thanks! :thumbsup:


WillyC24 01-21-2011 02:32 PM

Thanks, McMud! Did Ron give you a price on that mod to the head? Their "stock" 0331 head is $495.

mcmud 01-21-2011 02:50 PM

No, price was not discussed.

johnson30 01-21-2011 08:32 PM

Hesco 4.0L head conversion Kit Price
Hesco's site is a little have to hunt for it. Even having bought the thing, it just now took me about five minutes to find it.

What you saw immediately was the price for the aluminum head ($1,995.00).

Way to expensive for me.

Here's the information from the website on the standard head. Hesco modifies the head to accommodate the 4.2L intake, but they say they will weld the mounting studs on wherever you want them and that it can be reversed later to take the 4.0 intake. I was really happy with this- showed up at my door and I put it on. Done.

Cylinder Head Conversion Kit #HES4240CHC
Price: $1,150.00
Description: Converts the 4.2L to the 4.0L cylinder head using the superior 1991-up high port head casting. Designed to let your fuel starved 4.2L perform to its fullest potential. Provides a snappy throttle response with increased torque and horsepower. Complete bolt-on kit includes modified cylinder head with head gasket and valve cover. Will require a 4.0L exhaust manifold or header.
Part Number: HES4240CHC
Manufacturer: Hesco
Application 1: 4.2L Six Cylinder Jeep engines, to be converted to 4.0 head design.

WillyC24 01-26-2011 10:26 AM

Good discussion everyone, thanks. Three follow-up questions:

1) I've got a new 4.0L intake and exhaust manifold, so I don't need those mods. Is this head that Hesco sells already modified to accept the 4.2L intake?

2) Do you believe the 2x price difference with the Hesco is worth it over the Alabama Cylinder Head?

3) A bit of a random one, but what fuel pump would be most strongly recommended?

johnson30 01-26-2011 10:24 PM

Some opinion, some fact....
1) Hesco does whatever you want them to do, so to me that is a great advantage. They set it up for either the 4.0 intake or the 4.2, and they told me that if I changed my mind, I could have the mounting studs moved in the future, so I liked the sound of that.

2) I'd say that having the head delivered with the water jackets filled, a new valve cover, valve cover gasket (the metal and rubber type- not cork), and really expensive head gasket (it's the metal kind, with several layers...the factory gasket is more like one layer with some kind of felt on it....the Hesco gasket is clearly a high-pro version). So if you add up all the trouble of getting the modifications done, and finding and buying the upgade parts, I'd say yeah, it is worth it. I got the thing in the mail and installed it. Bing bang boom. Add it all up and compare- you are still paying more, but for me it was paying to remove a headache. You do need to buy new head bolts for a 4.0, something else I mistakenly forgot in my excitement.

3) I used a weber carb, so not sure from you saying that you have a 4.0 intake if your intent is to do a full MPI swap, but I'll give you my experience whether it helps or not (might help someone): I maintained the factory pulse fuel pump, and I wish I hadn't. I had to use a fuel regulator, and the fuel lines go everywhere because of mounting locations, and I still have the hard fuel line that runs over the valve cover (which I hate), and the pressure gauge pulses, so my perfectionist self wishes that I had coughed up a couple bucks for an electric fuel pump for the weber, which I know is available.

Maybe someone else can answer this one for the MPI if that is your intent.

The time now is 01:45 PM.

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