4.0 head, fuel economy - JeepForum.com
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post #1 of 3 Old 08-10-2004, 12:44 PM Thread Starter
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1981 CJ5 
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4.0 head, fuel economy

Has anyone out there swapped a 4.0 head on his/her 258? I'm thinking about putting a 4.0 on my 232 and I want to know if I'll see increases in fuel economy as well as increases in power. Currently I'm getting about 16 mpg.



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post #2 of 3 Old 08-10-2004, 01:05 PM
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1980 CJ5 
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I wonder if it would fit. The 4.0 head fit only 81 and later 258's and the 232 is similar to the earlier 258.
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post #3 of 3 Old 08-10-2004, 04:52 PM
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1986 CJ7 
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I wonder if it will fit also. I didn't know there was a difference between the 81 and later 258 blocks.

I have the 4.0 HO head (7120 cast) and see about 15 mpg with 4.10 gears and 31" tires with T5 trans. I drive with a pretty heavy foot so I'm sure I could squeeze a couple more mpg but it wouldn't be as fun. The head mod ain't for mileage but some poeple see some good gains when running a FI setup.

It's just a Jeep, and if you don't wheel it once in a while, it's not even that.
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