[eche981]

I found some parts for the swap last week . I found it all for 175.00. I need to know what parts i am missing for the swap. This is what i have.

1 4.0 head
1 4.0 valve cover
1 4.0 computer
1 4.0 wiring harness
1 throttle body
1 4.0 intake manifold
1 4.0 exhaust header
1 4.0 fuel rail
11 injectors
and a set of 4.0 push rods.

So the question is what parts do i have left to buy to get this thing running? Also do i need to swap out the cam?

[Burnerman]

You need to do a google search. You'll find what you need. I think putting the FI on is going to lead to alot more parts. You'll need a fuel pump, for one ,and rig up a CPS. Plus a whole lot more....

[YJRoller]

You will also need to have the water ports welded shut on the 4.0 head. Then have it remilled back to flat. It is an easy 30+ hp mod. But ya gotta do it right.

Do not do this fix

"The first step is to prepare the head for installation. After you've obtained all the parts from the parts list, you will need to perform the following task. In order for the 4.0L head to work on the 4.2L block, I had to fill in a couple of water jackets in the 4.0L head. They are the small triangular water jackets on the same side as the intake. These must be filled because on the 4.2L block these water jackets don't exist. I made a couple of calls and came to the conclusion that the best way to fill these holes is to use a high temp epoxy putty. I bought two tubes of QuikSteel. This is a 500 degree max temp super strength epoxy putty found at most auto parts stores."

Get a head that was professionally done. Like this one

http://cgi.ebay.com/ebaymotors/AMC-JEEP-258-4-0-H-O-Conversion-Cylinder-Head_W0QQcmdZViewItemQQcategoryZ33617QQihZ024QQite mZ370054977227QQrdZ1QQsspagenameZWDVW

[zeus87gn]

Ok, since the subject was brought up, why do these holes have to be filled?

If the water jacket holes don't exist in the 4.2 block, wouldn't the 4.0 head gasket seal them straight to the block? Or the 4.2 gasket seal them off right at the head?

Just looking for opinions and experience here.

[Douglas S.]

i think the holes are too close to the edge to be left unfilled. Also, i don't recommend you weld the holes because it could cause some serious warping and even more milling would be required. When i did this swap i just used j and b weld. I'm very happy with my results

before:


after

[zeus87gn]

Douglas,

Nice work!
I see your 4.2 intake manifold bolted right to the 4.0l head.
This is what I have planned as well.
Did you hae any problems with the manifold alignment?
Did you get the expected 30-40Hp gain with your carb setup?
I have heard of the JB weld trick and was going to try it.
I will guess you haven't yet experienced any leaks?
How old was your motor (mileage) when you converted?

Z

[YJRoller]

NICE WORK DOUGLAS!!!!

I have the same questions as Zeus. I have ben pondering doing this mod for a long time and this is the first actual person that had doc on doing it.

Please reply back to this

[Douglas S.]

Originally Posted by zeus87gn

Douglas,

Nice work!
I see your 4.2 intake manifold bolted right to the 4.0l head.
This is what I have planned as well.
Did you hae any problems with the manifold alignment?
Did you get the expected 30-40Hp gain with your carb setup?
I have heard of the JB weld trick and was going to try it.
I will guess you haven't yet experienced any leaks?
How old was your motor (mileage) when you converted?

Z

- The manifolds aligned very well for me, but i used the factory tubular headers off the 99 cherokee i pulled the head from
- i don't know exactly what i got, but the jeep is WAY WAY faster, it's almost like night and day
- i have no leaks so far
- i just did the swap a couple weeks ago and there are about 140000 km's on the motor

hope that helps!

only problem is getting a good pcv valve gasket for the 4.0 head, haven't really solved this yet

[zeus87gn]

Originally Posted by Douglas S.

- The manifolds aligned very well for me, but i used the factory tubular headers off the 99 cherokee i pulled the head from
- i don't know exactly what i got, but the jeep is WAY WAY faster, it's almost like night and day
- i have no leaks so far
- i just did the swap a couple weeks ago and there are about 140000 km's on the motor

hope that helps!

only problem is getting a good pcv valve gasket for the 4.0 head, haven't really solved this yet

You have the newer model head. I have one of the old 4.0HO heads waiting to be built in my garage. Freshly machined, just bare. I don't think there are many differences. I was more concerned with the intake alignment. But if yours bolted up, mine should too!
The exhaust manifold must change, I know this from looking at the head. The ports are completely different, and the 4.0 exhaust manifold is much better than the 4.2 by far!

140k Km is right at 87k miles. That's a relatively young motor.
I guess the PCV valve is a different OD than the 4.2?

Yes it does help!
Thank you very much for posting!

Do you think you have helped your fuel mileage?

[Douglas S.]

haven't really had a chance to check the mileage but it seems better.

[eche981]

so overall what i am getting is that i can use the existing 4.2 intake manifold on the 4.0 head!! If this is correct, what pushrods do i use the new 4.0 or the old 4.2. Also the 4.0 header will fit with the 4.2 intake?. It is all a little confusing. If i can just swap the head and the exhaust manifold out till i get the rest of the parts for the EFI swap that would be great. Is there anything that i am missing here. I would love to do it ASAP. I have the motor 1/2 tore apart right now. Any help would be great. Thanks in advance......

[Douglas S.]

Originally Posted by eche981

so overall what i am getting is that i can use the existing 4.2 intake manifold on the 4.0 head!! If this is correct, what pushrods do i use the new 4.0 or the old 4.2. Also the 4.0 header will fit with the 4.2 intake?. It is all a little confusing. If i can just swap the head and the exhaust manifold out till i get the rest of the parts for the EFI swap that would be great. Is there anything that i am missing here. I would love to do it ASAP. I have the motor 1/2 tore apart right now. Any help would be great. Thanks in advance......

I believe i used the 4.2 pushrods, but I'm not sure on that one
I used the original 4.2 intake and 4.0 exhaust and it worked out fine

[eche981]

do i need the special washers that allign the head, or are the head bolts for the 4.2 the same as the new head. i believe that the 4.0 takes a 1/2 head and have been told that the 4.2 original was 7/16.

[JJ Jeep]

I have read the 4.0 head on the 4.2 swap and am now thinking of this setup instead of a V8 (have a soft spot for the old 258's). Sounds like a fantastic increase in HP and response and a fairly easy mod. My question is that it is sort of confusing on which model of 4.0 head works best. Also is the head froom an EFI 4.0 OK or are all 4.0's EFI ? Now I'm thinking that a nice clifford intake and header would really be sweet. I'm just wanting to get the best advice of fitting it all together.

JJ Jeep

[wendell]

They sell the heads on ebay welded up and ready to go for the swap.