4.0L Heads-what years are compatible?


Aubrey

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Hi....I'm new here but have enjoyed the material in the library and forums for a few years now, and have come to rely on trs to learn more about my truck. This is my first new post.
I run a beater 91 Ranger work truck with 4.0 that had cracked heads that I replaced with an aftermarket set. I also installed upgraded/quiet rockers and pushrods. The new heads fit/work great and the selling point by the machine shop was they had 5 lbs more iron than the Ford heads.
Now I'm looking at junking the beater and upgrading to a newer 4.0 Ranger and hope to keep and reuse the new heads and rockers. (I've heard that cracked heads are a common problem.)
What years will these heads fit? Are all the 4.0's basically the same above the head gasket? Will 4.0 heads fit a 2.9?
 
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AllanD

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The early 4.0 heads you have will fit '90-94, except Aerostar where they will fit '95's as well as SOME '96's

They will fit and function on a later 4.0 but they MAY have larger combustion chambers so on a '95-up engine they will reduce compression, and thus power and efficiency.


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Aubrey

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Thanks Allan. That's a great help.

I'm following the fast idle thread closely.....I have the same fast idle problem. Since the computer will eventually slow it down to 1000 rpm, at first glance you would think the idle speed solenoid thing is working, although I am wondering if they can wear some lower gear teeth only making it unable to slow down below 1000 rpm. Not sure how they work but assume it is a flat gear arrangement with a solenoid tooth pulling/pushing the gear along. The other expensive thing I have left to check is the MAF. Eventually we'll figure it out.
 

AllanD

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The idle air solenoid is just that, a solenoid, a linear motor actuating a poppet valve.

All it does is oscillate back and forth.

They are VERY prone to getting "gummed up".

Take it off the engine and blow it out with aerosol carb cleaner.


AllanD
 

woodyedmiston

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While I would always defer to AllanD - who is right about the heads by the way - the "4.0 rebuild" article in the Technical Library has some more info about the differences in the heads, blocks, cams etc. It's even got pictures for those of us visual learners.
 


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