My friend has 2 engines sitting in his warehouse. One is 4.0 minus the fuel injection. The second is a 4.2 out of a 79 CJ. Both engines are in good shape. Which would be a better engine for a CJ? He's thinking of swapping the 4.0 head onto the 4.2 with the thinking that with it's longer stroke, that would be the fastest, simplest and most economical way to more power. Doing a crankshaft swap into the 4.0 would yield more displacement but there are costs involved and he would probably end up using the carb and intake from the 258. what do you guys think? <img src="/forums/images/graemlins/kewl.gif" alt="" />

The head only swap may not be easy or cheap. Most times the head needs some welding to cover coolant passages that overhang the 4.2 block. The head bolts are likely to be different diameter also. Then the carb intake and exhaust manifolds don't zackly fit the shape of the new head either.
If I had all them components I'd spend the money and time and go with a stroker and full injection engine..
Or on the cheap I'd just install the 4.2 and be done with it.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

Thanks for the reply BJ,

There are some articles on the web where people have used stuff like JB weld to seal up the coolant passages. I guess that works OK?

I have a 4.0 engine I just want the head and exhaust from, if your interested in the fuel injection setup maybe we can work something out. I have read about the 4.0 head onto a 4.2. Eventually will try it, right now I just upgraded to a motorcraft carb kit and working on either a HEI or TFI ign. I think I will probably leave it at that.
drop me a pm if you think this might work for you

good luck
kerby

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ok those should give you a good base of what you would be in for in both instances. I also included a couple sites for parts and or kits for both types of builds.