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Old 09-20-2015, 12:18 PM   #1
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258 4.0 head conversion

I've been really considering doing the head swap on my 76 cj but I've read some mixed information on the stock intake manifold lining up with the head studs. Some articles and people say it bolts right up some say you have to grind the manifold to make it work with headers and some say you have to grind the manifold and sit it on top the stud so everything lines up. I haven't been into it yet to know nor do I want to spend the the money on the rebuilt head until I know either. If there is problems Can you just get the 4.0 intake manifold to go with the head and convert it to a carb? I don't like the idea of the intake sitting on top the stud is why I ask. Is there someone that makes an intake for this application already converted for a carb? Any information would be greatly appreciated thanks!
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Old 10-05-2015, 02:08 PM   #2
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I've done a few of these swaps, my YJ and another buddies yj and my dad's 75 cj5. All of them we used the 7120 4.0 head, 4.0l intake/ flex exhaust manifold, and a carburetor adapter from a guy named Mike Ehrmann. His number is 1-719-337-3977. The adapter cost $85 but was well worth every penny because of the ease of use. It is specifically for a motorcraft 2100/2150, which is what my friend and dad went with and I used the adapter along with another to install a DIY Junkyard TBI.

Now since my Dad's cj is close in years to yours, that means you'll have the 7/16" head bolts and the 4.0 head uses the 1/2" head bolts. On my dad's I drilled out the block and tapped them with my milwaukee magnetic steel hawg to get a perfectly placed 1/2 hole. On an old ford engine I used 1/2 to 7/16 spacer adapters which worked out nicely and should work on the 258 so no drilling needed. The summit part number is
TFS-51400419

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Build Thread 1989 YJ, (Soon to come: TBI 350, 4l60) np231 sye/wide chain/6 pinion planetary, D30 ARB & Ford 8.8 ARB 4.56, 31" rollers for now, bds 3.5" springs, 1" Boom Shackles.
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Old 10-05-2015, 02:27 PM   #3
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Here is the dry setup before the head was machined and I was dry fitting
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Build Thread 1989 YJ, (Soon to come: TBI 350, 4l60) np231 sye/wide chain/6 pinion planetary, D30 ARB & Ford 8.8 ARB 4.56, 31" rollers for now, bds 3.5" springs, 1" Boom Shackles.
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