4.2L 4.0L head swap Alternator bracket question

[mutt248]

Hi guys,

I just swapped the the head on my 88' YJ 4.2L with a EFI head from a 94' 4.0L XJ. When I went to bolt up the alternator bracket to the block it does not match up. Can anybody tell me what bracket will work, Should I be looking for an alt. bracket from a EFI YJ? Will this resolve the problem. let me know.

Thanks!

[bbarrett]

the bolt holes are about 1/2 to 3/4 off, What i did was enlarge or oblong the bottom hole and cut the top out of the top hole, The top bolt will still catch plenty of metal. If u need me to i will take a picture tomorrow. Been fine for two years now.
Didnt notice this was posted april 20th. oh well may help someone else.

[Jeep-Power]

Mutt-
I'm surprised the OEM bracket didn't line up-- all of the brackets on my 4.2 mated right up to the 4.0 head, when I put it on. It was amazing-- as if the AMC engineers had it in mind.

[james.asaro]

Hi all, I am new to this forum. I am not sure if these questions have been answered in a previous forum, if so please let me know. I am interested in doing the 4.0l head swap onto my 89 YJ 4.2l. This is what I think I know so if you have actually completed the swap, can you please give me some backup:

1) I have read that I can only use a 4.0L HO Head from a '91 or newer 4.oL engine (Casting 0630 or 7120), and that I cannot use a RENIX casting).

2) I have also read that I will need push rods from the 4.0l head. The rocker arms from the 4.2l head will work.

3) My questions are:
a. Can I use my existing intake and exhaust manifold? I have read conflicting answers on this.
b. Will my alternator and PS brackets work (I have a v-belt setup without AC)?
c. I have installed a Howell TBI. Will this work for this application?
d. I will need a 4.0l head gasket. Do I need to use the copper spray on this? I know you need to for the 4.2l, but am not sure when this mod is done.
e. Aside from the head, I will need a 4.0l valve cover and gasket, a 4.0l exhaust and intake manifold gasket, and new head bolts. Is this all?
f. When I am doing the swap, can I replace the lifters? I am not planning on changing out the cam shaft. I have read that you can change this lifters without the cam shaft because the lifters are a much softer medal, but I would like to hear it from soneone who actually did it.

Thank you for your help.

Jimmy

[Jeep-Power]

Welcome Jimmy-

1) - I am 99% sure that is False. As far as I know, you can use any 4.0 head. Most folks go with the later '91 & up heads because the later EFI's are, for whatever reason, more desirable.

2) - False. on both of the swaps I did, I used 4.2 rods.

3)
a- No. 4.2 manifolds will not work on 4.0 heads. There is also a few discrepancies between the 4.0 exhaust manifolds, but that is a different topic.

b- yes. In my experience, all the bolt holes are where they need to be. Very cool. However, see the posts above yours.

c- I can't see why not. You will just have to retofit it to a 4.0 manifold.

d- in my experience, the copper spray is always a good idea.

e- you will need all the stuff, from the block deck up-- including the manifolds (as mentioned above). The head bolts are iffy-- I am pretty sure the later 4.2's came with the same size head bolts as the 4.0's. My 4.2 had 7/16" head bolts and the 4.0 head had 1/2" bolts. no biggie. I just drilled & tapped the 4 corner holes in the block to 1/2" so that the gasket located properly.

f- yes, that is when the lifters can be taken out. I would not replace only one-- as far as I know, it is best to replace both at the same time. Besides, a new cam is going to have better performance than a used cam.

[Jeep-Power]

if you haven't seen it--here's a write-up on my second swap