Need to mill the head?

In replacing the headgasket (leaking externally but not internall) do I need to mill the head if it has not been overheated?
Thanks
BSD

Pull the head and take it to a machine shop and have them check the flatness.

I am aware that it is "preferable" that it be checked for flatness, however, I have neither the time or money to do that right now. My issue is more about weighing the long term impact. If it makes a significant difference, I would let it sit rather than make it worse. Hwoever, if I can just change the gasket, it would be prefered. Have any just changed teh gasket without milling it?
Thanks
BSD

Mill it anyway. More compression = More power

Yes you can just install the head gasket, however I would at least get a straightedge, and a feeler gauge and check for warpage.

Testing the head is pretty simple. Need a straight edge (as absolutly straight as possible). Check it in a square pattern (from corner to corner over the bolt holes) with a 0.003 inch feeler gauge. Then in an "X" pattern from corner to corner. If the 0.003 feeler gauge clears in any spot, check it again with a 0.006 feeler gauge. You are allowed 0.003 for a short bow (or dip) and 0.006 for a long bow.
I use a really thick piece of glass and a fine red powder. Set the head on there and rub it around a little, the low spots show up pretty quick. Finding a thick, near absolutly level piece of glass is the trick, mine came from an aircraft surplus warehouse.
I´ve reused some heads, with a bit more clearance than recommended (tightened 5 pounds over spec: with new bolts). Made sure I used a coated gasket and added a little extra sealer near the water jacket and oil holes.
Also not a bad idea to check the bolt holes for a champfer. If you detect a high spot at the bolt holes (on the block), a little light work with a counter sink and a vacumn cleaner, will help with the seal. Can also use a fine (long) file to work the high spots, lightly (don´t get carried away, I usually stop before I scratch the block up much).

Thanks for the info guys. Actually, I am not working on my XJ but helping out a fellow coworker who is doubly cursed....he is neither mechanically gifted nor financially endowed. I guess there is one benefit of being broke most your life, you learn to get by.
Thanks
BSD

If it's someone else's vehicle, you really should explain to him that the correct procedure is to have a machine shop check the head for flatness, and mill it if it's not flat.

If HE chooses not to do this in order to save money, then he can't really blame you if there's a problem later. If YOU tell him that it's not necessary, and there is a problem down the road, you'll get the blame (and rightly so).

Eagle said:

If it's someone else's vehicle, you really should explain to him that the correct procedure is to have a machine shop check the head for flatness, and mill it if it's not flat.

If HE chooses not to do this in order to save money, then he can't really blame you if there's a problem later. If YOU tell him that it's not necessary, and there is a problem down the road, you'll get the blame (and rightly so).

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Of course I would tell him. Dude, I'm not an idiot, just trying to help someone who is broke. I think I can handle the ehtics on my own.

BSD said:

Of course I would tell him. Dude, I'm not an idiot, just trying to help someone who is broke. I think I can handle the ehtics on my own.

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I wasn't arguing ethics, "Dude." You're the person who asked the question, I was trying to help YOU cover your six o'clock.

You started off asking us a question without giving us all the pertinent information, then you get snotty when people try to help you. I don't know where this world is going these days. Sheesh.

The problem is they aren't thinking.. Its a jeep not a space shuttle. If its warped mill it, if its flat don't mill it. Even if it hasn't overheated it should be checked for warpage since you have it off. A warped head won't seal properly and your new headgasket will be worthless :lecture:

I doubt that machine shop would charge more than 10 or 20 bucks to check the head for flatness. Or, you could use the method suggested by "8mud", if you have the necessary tools.

In my mind, it's worth spending the money. If the head is NOT flat, and you put it all back together, your labor will be for nought, as the new head gasket will blow fairly quickly.

Given the price of head gaskets nowadays, I would say it's money worth spending.

Eagle said:

I wasn't arguing ethics, "Dude." You're the person who asked the question, I was trying to help YOU cover your six o'clock.

You started off asking us a question without giving us all the pertinent information, then you get snotty when people try to help you. I don't know where this world is going these days. Sheesh.

Click to expand...

Eagle said:

I wasn't arguing ethics, "Dude." You're the person who asked the question, I was trying to help YOU cover your six o'clock.

You started off asking us a question without giving us all the pertinent information, then you get snotty when people try to help you. I don't know where this world is going these days. Sheesh.

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Probably better to get a professional to do the measuring. But even if I´m gonna get some machine work done, I check it myself before giving it up and check it again when I get it back.
Have had some shops turn out garbage, heads milled thinner on one end than the other or excessive material removed. Not as critical on a straight 6, can really cause problems on a V-8.
I always check the block for flaws also, it isn´t always the head. I have seen some junk produced by the factory, that managed to hold together for years, you don´t even know the flaws are in there, until you take it apart, measure and eyeball it some.
Just a story, but had an old FSJ, sucker seemed to eat water pumps, every time I´d drain the radiator I´d notice some grains of sand in the bottom of the bucket. One day got feed up and wailed on the side of the block with a BFH and flushed it, got about two big handfulls of sand out of the water passages in the block. Moral of the story is, you really can´t trust anything but your own eyeballs and workmanship. Factory has been known to screw things up also. It`s most always, worth a look (and few measurements), before throwing good money after bad.
Back before milling machines,there was a gizmo called a milling file or head file. They used for about 50-60 years, before most anybody had access to a milling machine, outside of a production facility.

Listen to us old pharts....we been there. nuff sed.

Thanks for the feedback for those that recognized I was asking a technical question not an ethical one. Save the sermons for Sunday.
BSD