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Okay, so I've been told a lot of conflicting information regarding the correct way to re mate the head to the block of my 96 12v and it not blow apart 5k miles down the road.

Some context: I'm currently overhauling my stock 108k mile engine with some performance parts, most notably head studs, Hamilton 188/220 cam (lifters, springs, tappets etc), big turbo, and some other stuff. Needless to say, I'm going to be creating a bit more cylinder pressure than the stock engine ever experienced, so I want to make sure the head has the best chance of staying where it should for as many miles as possible.

I've been told by some people that "all you need to do is take a razor blade to the big stuff, and clamp that thing back on down" to "better make sure it's checked by a machine shop, decked, valve seats re-surfaced, and basically brand new if you want it to last". Obviously it would be better and safer to take the head to a shop and have them check it out, but I'm looking for the best balance of a cheap, and effective way of getting this thing back together.

So I'm asking the forums: Am I okay to just clean the head and block very well, knowing that the truck had absolutely no issues, and just put it all back together, or is it worth it to take the head to a shop and have them look at it. How many people have put it back together without checking flatness and or having it decked?
 

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I'm in a similar situation as well. I have the head off for a blown head gasket (bought the truck that way, so I don't know the real history). I've called around to five different local machine shops and have prices that range from $300 to $1200 for the same work. I don't really what to sink a bunch of extra money into it if I don't need to. Or get my serviceable head ruined by an incompetent machine shop.
So I'd also like to hear from those that have put it back together without having the head decked.
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FYI, a brand new more-or-less-stock fully assembled head is... shockingly cheap. <$600 shipped.
 

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That sounds like a plan to me. Where can I get a new head for $600??
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All you really need to do if your head was fine when you pulled it is take it to the machine shop and have them check the deck surface of the head to make sure its true and even. Thats the crucial part of whether your head gasket stays good for a long time or not. also if you have a cam I would advise going to valve springs that support that cam.
 

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That sounds like a plan to me. Where can I get a new head for $600??
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You are braver than I. I would never put a brand new head on that wasnt fully checked out by a machine shop. To many variables to a head for me to expect it to be 100% from any online dealer.
 

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I find it kind of odd that someone has the mechanical ability to rebuild a motor but not the sense to pay a machine shop a couple bucks to check a head for flatness to save a tear down in the future. All the money to blow on a big turbo and sticks but can鈥檛 scrounge the $100 for some piece of mind. I would not buy the turbo and make sure the head is good if money is the issue.
 

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Might have to go old school on it and break out the valve lapping compound and suction cup for the valve job then.
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I find it kind of odd that someone has the mechanical ability to rebuild a motor but not the sense to pay a machine shop a couple bucks to check a head for flatness to save a tear down in the future. All the money to blow on a big turbo and sticks but can鈥檛 scrounge the $100 for some piece of mind. I would not buy the turbo and make sure the head is good if money is the issue.

Two different trucks there. One is a working , relatively nice truck. The one I have the head off of is a beat down (and broken down ) old farm truck.

And money isn鈥檛 the issue, the fact that I want to keep my money is the issue.

If it were $100, not a big deal, but $700 is the average going rate in my area for a crack check, valve job, and deck surfacing. That鈥檚 almost half of what I paid for the whole dang truck.
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Two different trucks there. One is a working , relatively nice truck. The one I have the head off of is a beat down ( (and broken down ) old farm truck.

And money isn鈥檛 the issue, the fact that I want to keep my money is the issue.
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It鈥檚 a step that should be done. Is what I鈥檓 saying. Just like tearing down a good motor and just doing a hone. You can鈥檛 make the decision without the proper steps to insure that the parts are still up to the task. I don鈥檛 rebuild engines for a living and have only had a couple apart. But I know I will never pull a head and re install without ensuring a perfectly flat surface.
 

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So I'd also like to hear from those that have put it back together without having the head decked.
Me. I had the common seep under the t-stat and got tired of adding coolant when I had 195k on the truck. I pulled the head, cleaned the surfaces with a razor blade and scothbrite pad, check for flatness with a carpenters (not a machinist) straight edge, reused the original bolts and put it back together. It took me two days by myself in an unheated garage during a Christmas pause of work. The next time the head came off was 600k miles later. However, no fancy cam, no big injectors, no aftermarket turbo, no crazy timing. AND, I had owned the truck since brand new and knew it's history.
 
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Jegs has em. ProMaxx Performance CHR618N: Cylinder Head for Cummins Diesel 5.9L 6BT 12V Assembled | JEGS This came up in another thread some months ago and somebody mentioned this and I was pretty surprised at the $, but the reviews seem pretty solid. No personal experience with it though.

Man, now you got me flip-flopping like a politician.

I had settled on just checking the flatness with a straight edge and feeler gauge, then doing an old school suction cup & lapping compound valve job and calling it good.

But now seeing a completed new head (with good reviews) ,from a reputable company, for $554.99 (and free shipping), I'm re-considering
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That class of new aftermarket head should be surfaced before using. I've seen them out of flat by .005" and the surface finish from the factory is terrible.

Unless you're going to surface the head and the block at the same time, I would avoid surfacing one and not the other. Whatever distortion occurs to the parts often occurs in such a way that the head and block can be regarded as a "mated pair." I mean they're obviously not lapped together like valves and seats are, but take my original 5.9 for example:

There was a longitudinal bow of .008" in the block, and the head surface was crowned in a complimentary manner. If I had surfaced just the head without the block, the ends of the block/head would have touched and there would have been an .008" gap between them between cylinders 3 and 4. The head gasket would have sealed enough to have a viable engine, but based on what I've seen from similar build attempts, I probably would have started losing head gaskets if I'd pushed the power much past 400 or so when stock head gaskets and ARP 2000 studs can reliably handle 600+ when both surfaces are true.

If the block is crowned instead of bowed, you can get away with a lot more. For whatever reason, the head seems to distort more readily when pulling them onto a convex deck surface as opposed to a concave one. I'd be a lot less concerned about stretching a head over an .008" crown as opposed to trying to pull it into an .008" valley.
 

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I think if you are planning to have a more-or-less stock HP/boost truck... I would buy a $40 machinists straight edge off Amazon, check the head and the block, and then decide what to do from there. If it's close enough to true (or as d89 mentioned... if the 'off'-ness is matching between the head and the block :) than I would replace the valve seals, bolt it on, and call it a day.
 

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I think if you are planning to have a more-or-less stock HP/boost truck... I would buy a $40 machinists straight edge off Amazon, check the head and the block, and then decide what to do from there. If it's close enough to true (or as d89 mentioned... if the 'off'-ness is matching between the head and the block :) than I would replace the valve seals, bolt it on, and call it a day.

The kids truck is gonna be more or less stock. It'll have the free and cheap upgrades ( gov springs , valve springs, home ground fuel plate and so forth, just to make it more drive-able as these things are dangerously slooooooow in pure stock form).

I already bought a machinist straight edge from Amazon for just this project. Haven't gotten around to using it yet because we had some out of town visitors for the holiday weekend (and they're still here actually) and my head gasket kit still hasn't arrived (the gasket kit is getting dropped shipped straight from Mahle, and apparently they aren't real quick about shipping).

The major reason I wanted to drop the head off at a machine shop was a crack check/ magnaflux. I don't know the history of this engine, I'd hate to do all this work to a cracked head.
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I finally got around to removing the exhaust manifold & turbo and cleaning up the head. Overall the head is pretty dang flat. I couldn't get a 0.05mm (0.002 inches) feeler gauge under the machinist straight edge anywhere.

But I still decided to take it down to a machine shop and have it magnafluxed /cracked checked, and get the deck skim cut. While its flat, there is a ring around the combustion chamber that you can see and feel when you drag your fingernail across them.

Since the head was relatively flat to begin with, I don't think I'm messing up the match pairing by having it skim cut (at least I hope I'm not). We'll see, the machine shop has about a two week turnaround time so it'll be awhile.


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Discussion Starter #19
Update: I ended up taking the head to a shop and they had to take 0.010 off the head. Other than that it was in great shape. Really glad I bit the bullet and had it checked because I probably would have been looking at a blown gasket further down the road. Thanks for all the suggestions!
 
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