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+--- Thread: Single use cylinder head (/showthread.php?tid=4721)
Single use cylinder head - tree98 - 06-27-2019
Just wondering why the isx head is a throw away part? Exactly Why can't it be re machined and re used? I'm not at all disputing the fact that it can't, I'm just curious what the reasons are. People have recently asked me why I said not to re use the head, and I didn't really have a great answer, just trying to educate myself on the matter.
RE: Single use cylinder head - Lonestar10 - 06-27-2019
The proper way to rebuild the head to a new like state requires a stupid amount of machining and super expensive high precision machines/tools and if done correctly costs more than a new head from my understanding of what I've read. It's not a magnaflux/plane/new valve seats job it's requires much more to take the abuse it's given.
RE: Single use cylinder head - Lonestar10 - 06-27-2019
It's also my belief something as dense of a cast can only take so many heat cycles before it becomes so brittle that it becomes a liability.
RE: Single use cylinder head - dhirocz - 06-27-2019
My understanding is, and keep in mind this is lots of heads, not just the ISX, is that there arent that many people doing a quality job anymore. They just want to do a quick job and you end up with a pile of crap. To do it at a minimum, you would want to strip it, magnaflux it to check for cracks, machine it flat, do a valve job...we havent even discussed all the possibilities (like injector cups or pressure testing it). By the time you put all the money into it to legitimately make it right, you could get a new head.
Lots of times a reman has knurled guides instead of new, lapped valves instead of a valve job, and only springs that fail a pressure check or are damaged get replaced. Ive even seen a head resurfaced on a belt sander. Something like that is something I would expect on an engine rebuild on a 1960 checker taxi in Cuba, not a $3500 head. How much was machined off to make it flat? Is the RA correct for the head gasket? How thick is the head surface after machining? At least with new you know its all new which is far better than 'within spec' which by todays standards is a fairly wide margin.
Many shops out there doing half ass work now to cut costs because people aren't demanding quality (or dont know what quality looks like) and are easily fooled. Hell, most people would rather buy a chinese chevy head rather than spend the money on good stuff or at least have an OEM head done right. Then they wonder why they drop valves and the power was lousy to begin with.
Bottom line is while it is possible to get a decent reman, costs to do it RIGHT make it prohibitive (think of how many valves are in an ISX head), lots of the cores end up as ragged junk or are cracked to begin with before they ever come off (run until she blew), and many of these heads are simply 'remanned' by shops that do it 'good enough' to be 'within spec' before sending it out as fast as possible. They expect people to say 'enh, its got a warranty, right?' and then pull out their wallet without knowing what all goes into a properly rebuilt cylinder head.
Not on my engine.
RE: Single use cylinder head - tree98 - 06-27-2019
At some point the supply of brand new heads for 870/871 will be gone, then 2250/2350 will also get used up. I highly doubt Cummins is still manufacturing new heads for the older engines are they? So what will we do once they are all gone?
RE: Single use cylinder head - Rawze - 06-27-2019
4 of 5 will fail a magna-flux, ex-ray, stress, and proper pressure tests by the time they get 450k miles on them. At even higher mileage, there is no sense in putting a single dime into all those proper tests and checks alone, nonetheless doing any machining work on it, I don't care what the quality of work they do it is.
More likely to fail than not, at high mileage, it IS going to fail one of these tests. Most shops cannot even perform these tests properly, do not have full methods meant for testing commercial heads, etc. nonetheless, could correct these types of problems successfully for long term use. it is a commercial engine,. not your grandmothers 454-chevy. The standards for commercial engines are nowhere near the same a they are for cars... Hence why they are expected to last a million miles instead of a hundred thousand miles.
-- Because BOTH OPTIONS are still in the several thousands of dollars range (if you did get it done actually right by some damn lottery-winning miracle),,.. There IS STILL the consideration of that fact that it costs the typical truck owner upwards of $10,000+ or MORE to replace the head if were not to last as long as a new one. -- It is a far cheaper, and wiser investment to just buy a certified OE reman or get a new one, considering there is not that much difference in price byt the time you get one in your hands again.
Lastly,.. I have yet to meet anyone who said their re-machined head lasted more than a couple hundred thousand miles before it had rto come off for injector cups, or excess valve seat wear, or some other thing that made an engine problem of some sort.
If you want a definitive, short answer then -- It is simply... the "before-1-million-mile failure" rate is consistently too high, even by top quality high-end machine/head shops vs new OEM and the cost/savings difference cannot justify the risk of a $10,000 repair, consiodering a machine head will typically only last about 25% - 30% of the time/miles of a brand new OE head would last.
RE: Single use cylinder head - dhirocz - 06-27-2019
Good point in regards to heat cycles and the head being iron. That would also be something to consider. When you get something rebuilt, you really dont know its history. Playing Russian roulette kind of sucks.
Cummins makes new heads and 'throws them in' with the remans. They have to, because so many cores are useless for anything beyond a boat anchor. Thats my understanding of it anyway. I had to do some asking around last year to learn how to identify the new ones vs the remans. I had asked about an nx head before and was told flat out that they werent available.
Typically I wont use a head core or any cores really for any of my projects unless I know where it came from or its history at least. Too many bad ones. When it comes to my truck, however, new is the only way to go. Like Rawze said, a head is a $10k+ repair, so it really isnt worth the risk to save a few bucks in my opinion.
4 out of 5 by 450k? Wow. Those are horrible odds for something like a cylinder head.
RE: Single use cylinder head - Magard - 06-27-2019
I believe a remain might be new casting but used in spec valves and springs. Look forward to a dropped valve with a reman head. Especially if your jakes are set a little high. Speaking from experience.