4.2 or 4.0 build

[dan-cj7]

I'm planning my Cj7 restoration at the moment. I have the original 4.2 from the CJ and I have a 93 YJ I am using for a parts car. Both engines are useable as rebuilds. I was planning on using the YJ 4.0 with the AX15 and build a stroker with the crank and rods from the 4.2.

There is lots to read about the HP gains building a 4.6 stroker, but I haven't found anything that says what sort of HP there is possible by using the 4.2 lower end and swapping to the 4.0 head and fuel injection.

What problems should I be aware of putting the AX15 on the 4.2 crank?

Any advise?

Thanks,
Dan

[SilverXJ]

Not worth using the 4.2 bottom end.

[gradon]

4.2 bottom end with 4.0 head would not be as powerful as a 4.0 HO. You will have to get the correct size input shaft bearing/bushing to use the ax15 with the 4.2 crank. Early ax15s had .59" diameter input shafts and later ax15s had .75" diameter input shafts. I think by 93, they were .75".

[jeepman]

I agree that it is not worth doing the 4.0L head just swap the 4.0L into your CJ and as stated you have the parts if you want to stroke the 4.0L...

I installed a low KM 4.0L into my CJ7 a few years ago and Just the stock engine will make you happier then the stock 4.2L...

Remember the 4.2L is 110HP and the stock 4.0L is 190HP...