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4.0 issues


April 1, 2020
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City, State
Wichita, Kansas
Year, Model & Trim Level
91 explorer xlt 4x4
I have a 91 explorer limited. My 4.0 blew up just a couple days ago. Cracked head or blown head gasket. There are no 1st Gen engines available in my area. I found a 98 running 4.0 that I can afford. If I stop down to long block and keep the 98 flex plate and used my 91 intake, will it work without a Christmas tree dash?

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I don’t quite understand the question, but I’m assuming you mean pulling the heads from the 98 and using them on the 91 right? There is a slight difference in the 98s heads, which I’ve attached for you (sorry for the viewing angle). I’m not sure if it will affect compression much, but it might make a difference in how the engine runs. Personally, I did the opposite, where I pulled a 4.0 out of a 92 for my 97, and the transition went smoothly. I think as long as you keep your upper intake manifold and some other necessities, you’ll be safe from a check engine light. Good luck! (Btw, the 97 head is on the left, 92 on the right)

It will affect compression. Put later heads on a first gen will cause a huge spike in compression, conversely, 1st gen heads on a later model will lower compression. It has to do with the modifications made to the heads and the use of flat top versus dished pistons.

Just buy some aftermarket heads, they are cheap enough, and it will save you the trouble of figuring out what's what. Or you can just pull the 98 engine and swap over the intake, don't worry about the camshaft position sensor, and change out the injectors. Plug the egr hole in the exhaust though.

To clarify. Im wanting to use the long block and heads from the 98 and the intake and fuel rails etc from my 91 motor

The only problem I can see you having has to do with the motor mounts and their brackets, since I know there were some differences between years. Otherwise, follow MrQ’s tips regarding the injectors and such. I’m no expert, but I think the rest should be straight forward. Your intake from the 91 should work just fine.

Just did this again, over the years I have re powered MANY old rigs using the ohv engines from later models
Never mix matching clean fire heads onto the older blocks and vise versa... we just use the entire long block from the donor

We just put a 99 OHV engine into a 94 ranger

You will use ONLY the long block from the 98 donor
You keep the 98 engine block and heads.
Install EVERYTHING from the 91 onto it.
You will need a gasket set for the 91, Mahle makes a good one available on Rockauto
You will use the 91 engine mount plates, the 91 fuel rail, sensors, accessories, exhaust manifolds, everything.
Now a 98+ OHV has a 8 bolt crank
Your 91 engine has a 6 bolt crank.
If both engines are from the same type of transmission you are good to go. You said your 91 is a limited so I know it is an automatic. If the 98 was also an automatic then you are golden. If the 98 engine was a stick then you would need to order a 8 bolt flexplate in order to convert the 98 engine to fit automatic trans.

Make sure the 98 engine you are looking at is the OHV 4.0 NOT THE SOHC 4.0

Wait, do you mean Eddie Bauer? Limiteds were not released until 93.

No I mean limited. They badged as XLT but mine has many options available for limited only. I actually managed to find a 91 explorer in a scrap yard near me. I'm going to get the heads off it. The 98 motor is plan b. I have to replace all my tools. Drug addicts took everything out of my rig. Tools, stereo, clothes, scrap metal, documents...cleaned out. They destroyed my dash and couldn't get the head unit so they destroyed it too. Local law enforcement doesn't do anything about theft and my insurance won't cover it. I'm out another $4g so everything is now used parts

You have an XLT. Limiteds as a trim level were not offered until 1993. I know, I have one. The highest trim level before 93 was an Eddie Bauer.

I'm sorry to hear about your explorer getting broken into, I've had it done to me. 😟 Good luck with the heads.

Well it doesn't help that the hatch has the lock issue. I'm going to get a door switch and wire that in. I haven't been able to find a latch that wasn't overpriced.

I actually had two meth heads smash the window of my 2012 Ram when the found they couldn't hammer out the lock. Took my change, and my backpack with all my schoolwork, my laptop, and my tablet, and my goddamn spare glasses! And the stupid idiots left the GPS unit on the dash.

Due to this incident, I was out $250 for the glass, laptop was 3 years old but I had just put an SSD in it and it was a premium unit, so lets say $500, plus my tablet ($100), and I had to drop a class because I lost all my notes ($500), $7 in change, and $400 for the glasses. Total $1757. Total street value of that stuff was probably only a couple hundred.

So yeah a check for $500 from the insurance company didn't do squat. And I still want to kill the douchebags who ruined a good part of 2016 for me. :shoot: :splat:

I feel you. Problem with all my stuff is it was vintage and no longer available. I can't replace it with the same thing. My tools are replaceable and the head unit as well. The rest isn't.

Sorry your truck got broken into, that is the reason I do not lock my 2000 Ranger & do not leave anything of value in it.