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Unread 04-05-2010, 12:21 PM   #1
Timmy69
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4.2 to 4.0 head swap questions

ok so i currently have a 89 4.2l jeep and im doing the motorcraft cab swap but i think ive decided to go a different route due to the fact i have a 98 grand cherokee for parts that runs would it be more difficult to swap from this jeep compared to the 91-95 cherokees has anyone elso done so, what else would be involved?

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Unread 04-07-2010, 10:09 AM   #2
Timmy69
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cant anyone help me?
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Unread 04-07-2010, 11:05 AM   #3
RikRotorhead
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It was difficult to read what you posted without punctuation, but I think I know what you are asking.
The head swap is not difficult if you have the donor vehicle right there.
You will need the wiring harness and ECU from the donor vehicle. There are some modifications to the harness you will need to make.
The head on the 4.0 has water jets you will have to plug. That's easy too with some RV toilet paper and some JB Weld.
The exhaust system is different also. You can use the cat from the donor vehicle.
The computer from the 4.2 gets ripped completely out, and one side of the bulkhead harness will be replaced with the donor harness.
The end result will be something you will love. It's a huge difference.
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Unread 04-07-2010, 12:10 PM   #4
Timmy69
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Quote:
Originally Posted by RikRotorhead View Post
It was difficult to read what you posted without punctuation, but I think I know what you are asking.
The head swap is not difficult if you have the donor vehicle right there.
You will need the wiring harness and ECU from the donor vehicle. There are some modifications to the harness you will need to make.
The head on the 4.0 has water jets you will have to plug. That's easy too with some RV toilet paper and some JB Weld.
The exhaust system is different also. You can use the cat from the donor vehicle.
The computer from the 4.2 gets ripped completely out, and one side of the bulkhead harness will be replaced with the donor harness.
The end result will be something you will love. It's a huge difference.
ive read alot of swaps using the cherokee but nothing on grand cherokees i wasnt sure if it would make a difference or if it would pretty much be the same
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Unread 04-07-2010, 12:20 PM   #5
madmax79
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If you're switching to fuel injection, I think you would also need a new harmonic balancer and cut a hole in your bellhousing to mount a sensor. Do a google search and you will find some write-ups on the swap.
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Unread 04-07-2010, 01:38 PM   #6
RikRotorhead
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Quote:
Originally Posted by Timmy69 View Post
ive read alot of swaps using the cherokee but nothing on grand cherokees i wasnt sure if it would make a difference or if it would pretty much be the same
If your '89 has the AX15 trans, it already has the mounting hole for the crank position sensor. If not, you might want to consider putting the entire engine and trans into the Wrangler. If it does have the AX15, the flywheel will need to be changed from the cherokee because of the timing marks for the fuel injection.
Like I said, if you have the donor car right there, it will not be that hard.
The Grand Cherokee just has more cushy stuff in it. But the wiring harness is similar. You will be removing all the ABS stuff from the harness. There will be a lot of wires left over, because it doesn't take much to make the engine run.
Lots and lots of threads cover this subject. Just start reading before you dive in.
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Unread 04-07-2010, 04:11 PM   #7
Timmy69
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Quote:
Originally Posted by RikRotorhead View Post
If your '89 has the AX15 trans, it already has the mounting hole for the crank position sensor. If not, you might want to consider putting the entire engine and trans into the Wrangler. If it does have the AX15, the flywheel will need to be changed from the cherokee because of the timing marks for the fuel injection.
Like I said, if you have the donor car right there, it will not be that hard.
The Grand Cherokee just has more cushy stuff in it. But the wiring harness is similar. You will be removing all the ABS stuff from the harness. There will be a lot of wires left over, because it doesn't take much to make the engine run.
Lots and lots of threads cover this subject. Just start reading before you dive in.
i do have the AX15 and im in college so i cant just dive in ill have to wait about 5 more weeks to do so.Ive been reading about it quite a bit i just wanted to clean some things up. i was thinking of going FI but i havent decided yet becasue im worried about how much id be putting into the jeep if i did this. once again im in college so this means im broke haha.
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