258 with 4.0 head exhaust question

[clarkmac1985]

I am going to do a 4.0 head swap on my 258 and have a headman header already. was wondering if the actual port pattern is close enough that i can just drill new holes for the bolts and it would work. know the 4.0 manifolds are crack prone and im trying to kee the cost down as much as possible. also will be running the 258 intake for now but will be picking up a horseshoe intake and moding it for a 4bbl carb for future use. so can i MAKE my 258 header fit the 4.0 head?
btw its going on a 79 CJ7
thank you all for your responses and have a merry xmas

[SIXPAK]

I have not looked at that header for quite some time but I dont think it will work without some modification. The 4.0 number 3 &4 exhaust ports are spread apart. The intake will not line up the best either. You will have to raise the 258 intake to align the ports. You can relocate the holes in the intake. The dowel holes of the intake can be added to and redrilled. Some exhaust gaskets from each will show what you are up against. If you have some friends with some shop skills it is all doable fairly quickly. Merry CHRISTmas!

[ranger3157]

I recently finished swapping a 258 for a 4.6 stroker (began life as a 4.0 with 7120 head) in my Eagle. I was all the time thinking that my old (258) exhaust manifold would bolt right on up to the new engine and all would be well. Not so, not even close. I think that you will need a new header designed to fit your new 4.0 head. In addition, my understanding is that there was some variation in the 4.0 heads depending on production year. I have a 7120 head, stamped on the head casting right on top adjacent to the #4 exhaust port. I think there were at least two other head designs for the 4.0 engine , It may be that the header you end up with will be head specific.

[Russ Pottenger]

Mid generation HO castings 7120 or 0630 would be good choices and also be the most plentiful

[amceaglesx4]

Yea, lol the flange clearance between the axle bracket and driveshaft is really tight ! There really is not much room at all !!!

[Jeep-Power]

i was not able to use my Borla 258 hedder on the 7120 4.0 head. I looked into modifying the Borla to fit the 4.0, but it just wasn't worth the effort-- ended up getting a new hedder for the 4.0.

[amceaglesx4]

There isn't shit for room with the 4.0 exhaust manifold in the eagle. Between the axle bracket in the way as well as the driveshaft next to it. Even more of a bitch is getting half ass access to the flange bolts.