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Head change?

Head change?
Dep

Dep

Jeeper
Posts
129
Thanks
1
Location
ohio
Vehicle(s)
1985 CJ7, 258/4 speed.
The shop building my engine (1985, AMC 258 i6 / 4.2l ) called me with bad news. The head wasnt any good, had some cracks and was something like 25 thousand out? What casting numbers should I look for or does it matter? Head casting 393300, 591 C 27A.
 
I don't think the casting numbers are all that important if you are going back with the AMC 258 i6 / 4.2l head. The last time I had a AMC 258 i6 / 4.2l head built it took 3 cores to find one that was not cracked.:D
 
Sounds like it is a good time to do a 4.0 head swap, just a thought.
 
What's involved with the 4.0 headswap that i need to let the engine guy know?
 
Also, if I decide to go with some type of fuel injection hows the 4.0 headswap come into play?
 
There are a lot of wright-ups on this swap it's very popular and then you could use the stock Jeep 4.0 FI.
 
Are there certain castings that I should stay away from or look for?
 
If you could only do one mod on a AMC 258 i6 / 4.2l it would a 4.0 head. In my opinion anyway.
it does require a few other changes though like the exhaust won't swap over but that's another posive.:D
 
I did a 4.0 head & Howell TBI within the last couple of years along with a basic distributor cap upgrade. My CJ is mighty peppy!

Getting the right casting number is essential. I already cracked a 0331 head. I'm onto a 0630. 7120 is ideal. Certain blocks will need head bolt washers that you can buy from Clifford Performance.

In CA where emissions are strict, you'll need to modify your 4.0's exhaust manifold by adding a tube that goes into your intake manifold so that the EGR recirculates the NOx fumes. Hopefully you still have your EGR...or you live in a state that isn't so strict.

You'll need to tell Howell all the modifications that you've done so they can program the computer accordingly. They'll give you a new 4.0 prom also.

It takes a bit of time to round everything up, but it really does make the AMC 258 i6 / 4.2l much more enjoyable. Another good thing is that all of these parts are still readily available.
 
Is the "beefier" 0331 head that Clearwater Cylinder heads sells worth looking into? I have a few days of wiggle room with the shop working on the engine. Your set up is kind of the way I was headed with mine, basically stock, but reliable...
 
I have the 7120 with welded jackets from them I think it was. I would also recommend the xj aluminum valve cover, looks good and no more leaky gasket.
 
I also have a 7120 with a welded water jacket. I think it was from a 92 XJ at the PYP grave yard. My shop welded and milled it and did the 3 angle valves. It is a good thing.

Do your home work on this. You will also need new plugs, a later model head gasket, a header or the XJ exhaust manifold, special washers for the manifold bolts, if I am not mistaken head bolt shims as I think you have 7/16" head bolts and the head has 1/2" holes and new pushrods as the head is slightly taller. The last one is where you learn about preload on valves.:D
 
Dep said:
Is the "beefier" 0331 head that Clearwater Cylinder heads sells worth looking into? I have a few days of wiggle room with the shop working on the engine. Your set up is kind of the way I was headed with mine, basically stock, but reliable...
Click to expand...

I'm not familiar with the Clearwater Cylinder heads. Hesco's 4.0 seems to be the best one, but I don't think that the performance justifies the price. It's also on back order.

I am happy with the direction that I took with my CJ. It's updated under the hood and it didn't require a ton of work.

:chug:
 
MattandOrange said:
I'm not familiar with the Clearwater Cylinder heads. Hesco's 4.0 seems to be the best one, but I don't think that the performance justifies the price. It's also on back order.

I am happy with the direction that I took with my CJ. It's updated under the hood and it didn't require a ton of work.

:chug:
Click to expand...

$1100 for a 4.0 head?? Holey cow!! I paid $40 for the head and a couple of hundred to have it welded, decked and the valves ground. I did a port and polish on a previous project and really don't think that was worth the effort.:cool:
 
I have looked and called a lot of salvage yards looking for either a AMC 258 i6 / 4.2l or a 4.0 and I'm not having any luck finding either one . (Ohio) Not sure I want to throw $1k at a cylinder head for it. Other than this oppurtunity to replace it, its mostly staying stock....
 
I just ordered mine from Clearwater, $445 shipped. My 8 should finally be ping free ;)
 
I bought one from Clearwater about 10 years ago and it was OK I guess. It had bee repaired/welded where it was cracked between valves and the A/C mounting hole on the front corner had a helicoil in it. I used it all that time but it did end up cracking in the end at a different cylinder.

I guess the decision would depend on what you think your time is worth to pull and deliver to a machine shop. Some guys just fill the extra holes with JB weld, file it smooth and put it on the block.:D

I guess the trip to the grave yard would bring home the exhaust , valve cover and the push rods.:cool:
 
Dep said:
I have looked and called a lot of salvage yards looking for either a AMC 258 i6 / 4.2l or a 4.0 and I'm not having any luck finding either one . (Ohio) Not sure I want to throw $1k at a cylinder head for it. Other than this oppurtunity to replace it, its mostly staying stock....
Click to expand...


I find it very hard to believe that there was not a troop of Xjs sitting in anyof the jys you went to. I have yet to go to a JY and not see at least 2 of them. You can also look under the hoods of Grand cherokees as they had 4.0s in them. Personally I would use any year of 91+ 4.0 head. Everyone says stick to 91-95 heads because they flow better or something but I think that is just one of those things that someone said to do so everyone says to do it, that happens a lot with jeep mods. You would probably not notice the difference between a 95 or 96+ head on your engine. but you will notice a difference betweent AMC 258 i6 / 4.2l head and a 4.0 head.
 
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