Newer head to older engine questions

[Steve]

Hey folks,

I am dealing with a possible cracked/warped head on my 1990 Cherokee.

That thread is going separately, but I wanted to ask about a possible solution using parts i have.

I have a 7120 casting head from a wrangler with intake manifold, injection components, and throttle body. (I can take and post pictures if needed)

The questions are:

Can i swap that onto my dead stock 4.0? (after a rebuild)

Do i need to acquire a different exhaust manifold? If so which would be best?

My research shows there is an issue with the TPS that needs a mod but i have not found details of specifically what.

(Oh, it's an automatic)

The other option is to sell those parts and buy a used head to have rebuilt.

[89xjgrey]

Yes, your newer head will bolt up to the block. You will need to retain your idle air control valve, but it will fit the newer throttle body. You'll also retain your stock map sensor...disconnect the one off the new throttle body and plug the little port. You will need a '91 or newer exhaust manifold. I recommend this one...

Jeep Exhaust Manifold - iNeedParts.com

You also need to retain your current TPS. An adapter is necessary...some people make their own...but due to the simplicity of it, I recommend this pre-fabricated one...

Hesco Inc. - High Performance Engine Service

Good luck! That was my exact setup on my old '89!

[89xjgrey]

I forgot to mention, you may as well be prepared to install a new motor back exhaust system, as your current down pipe will not bolt up to the new manifold.

[Steve]

Thanks,

Woof... $150 for the manifold $150 for the adapter... I could just get a rebuild RENIX Head for that... Sorry. I'll have to look up the DIY adapter and a Junk yard exhaust.

My budget is thinner than an RCH.

I appreciate the help,
Steve

[4jeepers]

Originally Posted by Steve

Thanks,

Woof... $150 for the manifold $150 for the adapter... I could just get a rebuild RENIX Head for that... Sorry. I'll have to look up the DIY adapter and a Junk yard exhaust.

My budget is thinner than an RCH.

I appreciate the help,
Steve

Steve, Thats what I would do! Too many expensive mods. to make it worth while.

[5-90]

NOTA BENE:

You're here in CA, and therefore subject to the whims and dicta of the Air Police. You're going to run into trouble deleting the EGR system!

Check with your local smog referee. I know the cam didn't get changed 1990/1991, but the EGR was deleted due to the use of "exhaust port reversion" (did the same job, but without crapping up the intake with carbon and by eliminating a failure-prone part.)

The EGR is of limited utility on the AMC six anyhow - it's got agreeably low compression (both SCR and DCR,) so the NOx formation is agreeably low. In fact, I've got before/after reports around here somewhere that show that the AMC242 runs cleaner without the EGR setup than it does with, but that argument held no water whatever with CARB (I tried for a year. I don't like keeping unnecessary systems that are prone to failure...)

Forewarned is forearmed. You can find the office of a Smog Referee close to you by checking with the California Air Resources Board website (Google them - I don't have the URL handy.)

CA makes it such a pain to be a hobbyist mechanic...

[Steve]

Thanks,

I found this article which really kinda layed out what looks like the right process.

http://grannys.tripod.com/califlegalswap.html

I will contact a local ref just to be sure but most likely i will just get a used motor and rebuild the whole thing.

Steve