cracked head between 2 valves

will i need to get a whole new damn head or is this crack repairable? its between the 2 valves at cylinder #1 on my head

Get another head.

so its irrepairable?

take it to a engine shop, a good one should be able to fix it. pull the valves out to check how far in the crack goes

Not normally, it would be wise to pick up a used head and have it re-worked (cost is around $100 for a head and another $100 to turn and lap the valves around here)

What's the casting number on the head?

A cast iron head can be stop-drilled, pinned or welded, and ground flat - but between the valves makes it very difficult.

I'm assuming you're up in the Great White North. Pity. I'm trying to collect heads for experimentation, and I honestly don't care if they're cracked...

But, I'm going to say to get the head replaced as well - since cracks between the valves are a mother to get fixed (it's not impossible, but it will probably cost you about twice as much as a "flat crack" to fix by the time you're all done with the machine work needed...)

To be safe you need to replace that cracked head with another. I would never trust a weld on a cast iron head.

okay so any place to buy an aftermarket replacement relatively inexpensive?

tonexj said:

okay so any place to buy an aftermarket replacement relatively inexpensive?

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The only "aftermarket" replacement is the aluminum head being sold by Patriot Performance & HESCO (at last recall. There may be some more now.)

But, the beggar is spendy - expect to spend US$1600-1800 for the thing, assembled.

MUCH cheaper to find a decent boneyard head and have it reconditioned. If you check around, you can sometimes fine "dye-check" kits for finding cracks in metal parts for a few bucks, and you can check out the head before you pay for it in the first place. Even buying the kit (I think I picked up a couple for US$40 each or so,) will put you well ahead of the aluminum head.

There are, as far as I know, no iron "aftermarket" heads (new castings) available.

What year is your engine?

94', i found this though, will it fit?

http://cgi.ebay.com/ebaymotors/_Car....c0.m245&_trkparms=72:543|65:12|39:1|240:1318

tonexj said:

94', i found this though, will it fit?

http://cgi.ebay.com/ebaymotors/_Car....c0.m245&_trkparms=72:543|65:12|39:1|240:1318

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It should (it will bolt to the block,) but you may lose a bit of performance.

Ideally, you'll want a 1991-1995 4.0L cylinder head, XJ/ZJ/YJ/MJ. 1996-up started seeing reduction in the port sized (exhaust first, then intake) and that's why you end up losing performance. It won't be much (you probably won't notice it on butt dyno measurement,) but it's there. However, it should not be significant.

IIRC, the manifold attaching screw pattern didn't change 1991-2007, and the primary difference is in intake/exhaust port sizes and flow. You may find that the exhaust ports on the #7120 head are somewhat larger than the #0630 head you're looking that, but what you'd lose in exhaust flow is made up for in the reduction in exhaust reversion as a result.

Refresh my memory - isn't Windsor just across the border from the States, near Michigan? This is the first cracked #7120 head I've heard of, and I wouldn't feel guilty cutting the thing up (as I plan to do with one of each head.) I'd like to see if we can't come to a working arrangement to get the thing in here, and get it over to me. I don't mind doing it in pieces - if you have access to a metal chop saw or a bandsaw, or know someone on this side of the line who does, we can work something out...

no i live in windsor, california.

tonexj said:

no i live in windsor, california.

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Ah! That would make it easier for me to get the old head, if you don't need it for a core... And, you're not even that far away from me, it seems - perhaps we could meet in the middle somewhere?

Finish resolving the whole issue first tho - I doubt the head would be acceptable as a core, but they might want it (if you get a store head, do check - I know that core charges can see some serious deductions for things like this, and it may get to the point where it's just not worth the trouble to take it back in.)

Principally, sectioning the castings and porting experimentation. That's why I don't mind sectioning the head - makes it easier to handle. As far as casting structure checkout, I'd be cutting a cylinder section of the head into 1/4" slices - I just want to do it myself so I can take pictures as I go (using a bandsaw, which should help keep the kerf down and give a better picture. And, I'll probably be taking measurements as well while I'm doing it.)