4.2 intake on 4.0 head? Head swap problems! - JeepForum.com
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post #1 of 28 Old 03-29-2010, 06:52 PM Thread Starter
grimjeeperyj14
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4.2 intake on 4.0 head? Head swap problems!

I was told somewhere that I could make the 4.2 intake work on the 4.0 head. How was this done, the gaskets dont match up, and has circle ports intead of square ports. I have everything all the other parts for the head swap but this is holding me back. I also have an aftermarket 4.2 performance header can I make that work too?


Driving my Jeep is uncomfortable, loud and drafty.... and I love every minute of it
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post #2 of 28 Old 03-29-2010, 08:24 PM
ElvisV04290
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You need a gasket for a 4.0 head. The 4.2 intake will match up to that. My guess is the gasket you are using is for a 4.2 head. And you can't make the 4.2 header work, you need a 4.0 one.

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post #3 of 28 Old 03-29-2010, 08:24 PM
dblakey
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The intake will fit. I cant remember exactly how, but when i did the head swap on mine a few years ago, I used the 4.2 carb intake and a 4.0 header. I remember grinding a little on the intake to allow it to locate properly on the head, but can't remember where. Also, I remember having to grind on the power steering bracket for clearance of the header. The port mismatch is not that big a deal considering the rpms you will be turning. The swap makes a huge increase in torque and upper rpm hp. There should be a lot of info on this somewhere.

Sorry I can't remember, but I can tell you it does fit.
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post #4 of 28 Old 03-29-2010, 08:35 PM
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Here you go, search engines are your friend.
4.2L Head Conversion - Putting a 4.0L head on a 4.2L block!! - Jeep at Off-Road.com

Dwayne


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post #5 of 28 Old 03-14-2011, 09:38 PM
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no more pics in that link

I don't feel like working on anything at this time so i sold my yj.
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post #6 of 28 Old 03-15-2011, 08:23 AM
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Are you looking for something SuperJ. This is reviving a year old thread.
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post #7 of 28 Old 03-15-2011, 09:34 AM
superj
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just the pics. i was told my jeep had a cherokee motor in it when i bought it, and all the sensors were cherokee sensors but it doesn't look like one. and then if it is a 4.2 instead of a 4.0, i want to do the head swap

I don't feel like working on anything at this time so i sold my yj.
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post #8 of 28 Old 03-15-2011, 10:41 AM
Que89YJ
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Cherokee sensors? The only difference between the 2 is the temp sensor electrically.
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post #9 of 28 Old 03-15-2011, 12:03 PM
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Quote:
Originally Posted by superj View Post
just the pics. i was told my jeep had a cherokee motor in it when i bought it, and all the sensors were cherokee sensors but it doesn't look like one. and then if it is a 4.2 instead of a 4.0, i want to do the head swap
easy enough to tell, ones is carbed one is FI... look at the engine, that part is simple....

Started with some rust repairs ended in a SOA...


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post #10 of 28 Old 03-15-2011, 03:37 PM
superj
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I know that part but I have read you can put the carb stuff on the injected motor (if you want to go backwards). Mine has all the bolt on parts from 4.2L engine on it so I don't know what to look for to tell if its a 4.0 or 4.2. I've got a serpentine belt, aluminum valave cover two holes on top of the valve cover for pcv or something and I was told the engine was swapped from a 99 cherokee. That is what I am trying to verify

I don't feel like working on anything at this time so i sold my yj.
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post #11 of 28 Old 03-15-2011, 05:39 PM
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I dont know why anyone would go backwards to a carb setup....... if its is a 4.2 it will have a mech fuel pump on teh pass side down by the dist just in front, either had to keep it and use it or block it and use a electric fuel pump which would be mounted on teh side of the frame somewhere prolly.... if its a 4.0...? I dont know

or maybe its just a 4.2..... it wold make more sense for someone to do a stroker IF ya had both a 4.0 and 4.2.... but to go backwards to a carb setup dont seem like a viable thing to do

Started with some rust repairs ended in a SOA...


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post #12 of 28 Old 03-15-2011, 07:43 PM
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I know but because of the small town the jeep is from, its very possible they did that.

Ok, no mechanical fuel pump on the side of the block. It had a crappy mr. Gasket pump on the fender which I swapped for a nice holley low pressure pump. That is some thing I never knew, that the factory pump was down by the distributor on a 4.2. So that's easy then, no pump on block. Does that automatically mean its a 4.0 block or did all 4.2 have engine mounted pumps? How do I recognize the head? Any little trick like that to find out which head I have?

Thanks guys, that is a hell of a bit of help you have given so far

I don't feel like working on anything at this time so i sold my yj.
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post #13 of 28 Old 03-15-2011, 07:43 PM
superj
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I know but because of the small town the jeep is from, its very possible they did that.

Ok, no mechanical fuel pump on the side of the block. It had a crappy mr. Gasket pump on the fender which I swapped for a nice holley low pressure pump. That is some thing I never knew, that the factory pump was down by the distributor on a 4.2. So that's easy then, no pump on block. Does that automatically mean its a 4.0 block or did all 4.2 have engine mounted pumps? How do I recognize the head? Any little trick like that to find out which head I have?

Thanks guys, that is a hell of a bit of help you have given so far

I don't feel like working on anything at this time so i sold my yj.
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post #14 of 28 Old 03-15-2011, 08:37 PM
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the fact the pump was on the fender would give it away for me, normallly the pump is in the tank I beleive on a 4.0... so maybe used to havea 4.2 and now it has a 4.0, is it a fuel pump or fuel pressure regulator mountd on the fender..????

the 4.2 with a different carb calls for a FPR...

4.2 are carbed everything about them is mechanical, pumps are 18 bucks and a 3 minute job to replace, taht is the appeal to them THEY ARE EASYTO WORK ON... the 4.0 not as easy but not bad...

POST A PIC OF THEN ENGINE.....

soemone will ID it....

Started with some rust repairs ended in a SOA...


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post #15 of 28 Old 03-15-2011, 10:04 PM
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Just the swap 2 weeks ago. I took a rat tail file and made a half moon circles on the bottom of the intake dowl holes (they sit on top of the head dowls). Also had to heat up the 4.0 header and bang the front and rear tube in a little since the intake was hitting. Than I ground a little off one of the corners of the intake. Great fit. Used over size washers to hold the intake to the head.

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