Oi... Bring on the flame! 4.0 head swap ?

[Thunder81]

Hey guys Im sure I'll get toasted for this one. Bit of a newb here doing a 4.0 head swap. I've read all the articals and done a ton of research. Got a AMC 258 i6 / 4.2l for an 89? jeep YJ, picked up a 7120 4.0 head, and a header off an old cherokee... Now through all the stuff I've seen and read...
I'm unsure of what to do with that Cross over line from the exhaust manifold to the intake manifold? The exhaust header I have doesnt have one, but the intake manifold does... What do I do with this??? How do I block this off?
Thanks for any help.
P.S. This wont be the last dumb question I ask I'm sure.

 

[IOPort51]

the line in question goes to the EGR valve. block it off.
The EGr should do a good enough job of blocking it by it self but putting a plug in the tube hole couldn't hurt. I don't remember if ti is a pipe thread or something strange.

 

[gert]

If your gonna keep the carb set up it will be fun in the winter keep the heater hoses going thru the intake so it wont get to cold in the winter

 

[Thunder81]

Thanks guys.
I will be running a carb... and in the winter. Should I be worried? haha

 

[kickitandholdit]

lets see some pictures

 

[CJim7]

I ran this settup on my AMC 258 i6 / 4.2l along with a 500cfm Edelbrock. No EGR. This was in the frosty land of winter known as Montana and I didnt really have any problems outside of the normal carb issues....always a cold start anyways.

 

[Cheepjeep85]

I'm still on the stock head, intake, exhaust manifold and mine been plugged for a while. A brass pipe plug works I can't remember the size though.

Sent from my DROID2 using Tapatalk

 

[Rescue Diver]

Hey guys Im sure I'll get toasted for this one. Bit of a newb here doing a 4.0 head swap. I've read all the articals and done a ton of research. Got a AMC 258 i6 / 4.2l for an 89? jeep YJ, picked up a 7120 4.0 head, and a header off an old cherokee... Now through all the stuff I've seen and read...
I'm unsure of what to do with that Cross over line from the exhaust manifold to the intake manifold? The exhaust header I have doesnt have one, but the intake manifold does... What do I do with this??? How do I block this off?
Thanks for any help.
P.S. This wont be the last dumb question I ask I'm sure.

Why would you get flamed for a question?????

So you have the aluminum later model AMC 258 i6 / 4.2l intake and you're wanting to block the 1" round hole under the carb? If that's what you're talking about, I filled mine with JB Weld.

 

[Rescue Diver]

the line in question goes to the EGR valve. block it off.
The EGr should do a good enough job of blocking it by it self but putting a plug in the tube hole couldn't hurt. I don't remember if ti is a pipe thread or something strange.

There are two holes near where the EGR connects. One is threaded for a vacuum line. I'm using that one for my power brakes since it's so close to the booster. The other (lower) hole isn't threaded. That's the one I filled in with JB Weld because I don't live in the People's Republic of Kalifornia, and I wanted the manifold to look clean and simple. Even a cork would work fine to plug that hole if someone doesn't want to run an EGR.

 

[Rescue Diver]

Thunder81, one more thing to keep in mind if you're running the AMC 258 i6 / 4.2l aluminum intake manifold with a tubular Cherokee exhaust manifold. You'll probably need to put a small dent in the exhaust manifold to make it clear the intake. It won't be visible when assembled, and it won't hurt your performance.

Do you have power steering? If so, you'll need to either cut the out of your power steering bracket to clear the front exhaust manifold tube, or switch to a 4.0 serpentine belt setup with the 4.0 power steering pump.

If you're running a later model AMC 258 i6 / 4.2l block with the 4.0 head, you'll also need spacers for the head bolts because post 1980 AMC 258 i6 / 4.2l 's use a 7/16" head bolt while the 4.0 head has holes for 1/2" head bolts. All they are is a metal sleeve that takes up the extra space to keep the head centered. You'll also want to torque the head bolts to your AMC 258 i6 / 4.2l specs since they're a smaller diameter.

 

[Thunder81]

Thanks for the reply's guys. Just figured I'd get flamed cause it seems like a dumb question even to me... I guess I got lucky with the motor I picked up, its got 1/2 inch head bolts so no need for spacers, and lucky again that the AMC 258 i6 / 4.2l valve cover I got will bolt right onto the 4.0 head Score right? haha. I just finished putting the JB weld in the water jacket holes, that was easy, though I did have to drive around town for an hour to find Starch packing peanuts... D'oh. As for lining up the AMC 258 i6 / 4.2l intake manifold for the 4.0 head I just used the intake/exhaust manifold gasket for the 4.0, and notched the intake where the dowel holes were, so it should be perfect... I'll have a look for a brass plug, don't see why that shouldn't work thanks again.
I'm off to work for 4 more days so I'll do what I can to get some pics up next week. Probably gunna have time to put it all back together then. Guess I'll have a look at the P/S pump issue then. Thanks guys.

 

[Rescue Diver]

Thanks for the reply's guys. Just figured I'd get flamed cause it seems like a dumb question even to me... I guess I got lucky with the motor I picked up, its got 1/2 inch head bolts so no need for spacers, and lucky again that the AMC 258 i6 / 4.2l valve cover I got will bolt right onto the 4.0 head Score right? haha. I just finished putting the JB weld in the water jacket holes, that was easy, though I did have to drive around town for an hour to find Starch packing peanuts... D'oh. As for lining up the AMC 258 i6 / 4.2l intake manifold for the 4.0 head I just used the intake/exhaust manifold gasket for the 4.0, and notched the intake where the dowel holes were, so it should be perfect... I'll have a look for a brass plug, don't see why that shouldn't work thanks again.
I'm off to work for 4 more days so I'll do what I can to get some pics up next week. Probably gunna have time to put it all back together then. Guess I'll have a look at the P/S pump issue then. Thanks guys.

Oh that's right! Now I seem to remember that the AMC 258 i6 / 4.2l went back to 1/2" head bolts right before they switched to the 4.0. You said something about the AMC 258 i6 / 4.2l your using coming out of a late 80's if I remember correctly. With 1/2" bolts, just torque it to 4.0 specs.

Sounds like you've got everything under control with lining up the intake. Now all you have to do is make some plates for the bolts to bridge the larger gap between the intake and exhaust manifolds. Since you haven't installed the intake yet, why not just use a little more JB Weld to fill that extra hole in the intake? It's not threaded, so bolting in a plug isn't going to work unless you tap it. Since it's only a big vacuum port with the EGR removed, it doesn't take much to plug it.

As for the PS bracket, you'll need to grind a bug chunk out of the aluminum part of the bracket on top of cutting a big hole in the steel bracket. It'll eliminate the bolt that tightens it down so it doesn't piviot, but I found that as long as you tighten down the bolt that it actually pivots on really good, it won't move on you. After reading all about it from numerous sources on the net, I was really surprised at how much metal I had to remove to get it to clear the front tube of the exhaust manifold.


P.S. It really wasn't a dumb question.