I have an '83 CJ7 with the 258. The engine is in need of a rebuild but the the block is chipped up by the water pump so went in search of another block to rebuild. I bought what I was told was an '83 engine sight unseen but it turns out to be a '79. I know I know but for a $100 it was worth the gamble. So I am trying to sort out my options, 1) rebuild the '79 as is 2) rebuild the '79 block and use the '83 head and manifolds or 3) attempt to get the chip repaired and rebuild the '83 as is (extra $150). I have lots of questions but the one I have now is what is connected to the fitting in the pic (red arrow, '79 block)? That fitting does not exist on my '83. The '83 looks like it has a plug where that connector would be but it is a little hard to get a clear view of it since it is still in the Jeep.
My thought at this time is to just rebuild the '79 with the '79 head which is one of the reasons I am trying to figure out what goes to that connection because in its stock form it connects to something, I just don't to what or where. The only reason i considered the '83 head was because it was already configured for the aftermarket aluminum valve cover that is on the '83. The engine builder that i spoke to said he has drill out the 7/16 heads to put on the 1/2 stud blocks and was no big deal to do. I guess it is probably more straight forward to use the '79 head and have the mods done to it to accomidate the aluminum valve cover. I wasn't sure if there was any value in using the '83 head and manifolds over the '79 in general.
Forget the aluminum valve cover and then you don't have any machine work.
That fitting, which is the CTO valve (or what's left of it), is specific to '79 emissions and other parts which that year uses. You won't use it, but do swap whatever fitting is in your existing block to this one.
Yup, no big deal with the CTO valve. If you don't need it then have your machine shop just install a plug in its place or use it for a mechanical temp gage in its location. I would personally look into having them drill out your 83 head for 1/2" simply because of the aluminum valve cover. You will probably never find one for the other. The only manufacturer for it was Clifford and they stopped making them years ago and the 81+ won't fit because it is strait on one side and the early models had curves on both sides.