The excess cam wear mystery revealed.
03-05-2016, (Subject: The excess cam wear mystery revealed. ) 
Post: #1
The excess cam wear mystery revealed.
What do your cams look like? --


-- One big cause of pre-mature overhead cam wear is in fact NOT doing an overhead valve adjustment on a regular basis. Cummins recommends the overhead be done every 500k miles,.. but I have found this to be WAY TOO LONG of an interval. It actually needs to be done about every 200,000 - 250k miles or so. This is because the valves tighten up, not get looser, and eventually can cause the rocker to ride the cam all the time wearing it out. Performing proper overhead adjustments is a big factor in preventing excess wear, but there is a lot more to this story, so here goes...

Even with proper care and regular adjustments of the overhead valves,... It is quite well known that ISX engines do get premature overhead cam wear. For a long time, it has been a mystery to me as to why, and has been blamed on everything from improper oil changes to using synthetic oil and extended oil change intervals.

THE NUMBER ONE CAUSE!!!--- VALVES NOT ADJUSTED OFTEN ENOUGH AND/OR TOO MUCH SOOT AND/OR WEAR METALS RUNNING AROUND IN YOUR OIL!!! ...


THE NUMBER TWO CAUSE!!! --- NOT REPLACING THE CRANK CASE FILTER OFTEN ENOUGH AND ALLOWING PRESSURE TO BUILD UP IN THE ENGINE!!! ...


When someone allows too much pressure buildup in the engine, this is the number-2 cause of premature cam failures. This is because there is usually only about 8 or 9 psi of oil pressure at the rockers by the time the oil travels this high up. Because of this, it only takes a slight restriction in the crank case ventilation system to make this 9 psi only about 3 or 4 psi. - This will starve the top-end of oil and the rockers can run dry.

To prevent pressure buildup, replace the crank case filter with a maintenance free filter element. here is what one looks like: http://rawze.com/forums/showthread.php?t...50#pid8950

THE NUMBER THREE CAUSE!!! --- NOT CHANGING THE OIL OFTEN ENOUGH VS. THE ENGINE'S USE!!! ...



Problem#3: The problem that causes this type of wear is also the same problem that causes rocker shafts and rockers to wear prematurely as well. On an egr engine, not changing the oil and filters often enough also causes a lot of carbon packing in the engine. Soot and other deposits can very easily clog up the passages (cross-drillings) in the rocker shafts themselves, and the passages inside the rockers that feed the cross-heads.


Premature cam wear...
./uploads/201603/post_2_1457195623_6fd84208d7770a3b4c017f0e36d7f321.jpg



Rocker shafts starved of oil...
./uploads/201603/post_2_1457195753_7d187e80f94dfdb660565e39591e6485.jpg


And then the cams themselves get starved of oil too.
./uploads/201603/post_2_1457195718_379f708a09e82d1e88af61175fe7c780.jpg


What is happening is that soot, oil starvation, and/or deposits build up, restricting oil flow. when the rockers themselves get plugged up, and they also cause excess wear in the cross-heads quite often too.

Worn out cross-heads...
./uploads/201603/post_2_1457195745_62e2ff14d53270bf0b679424de4d05c4.jpg

Prevention and Cure...


The prevention IS to keep the soot and wear metals out of your oil, Keep the overhead valves adjusted properly so that the rockers are not riding the cams too much, and to absolutely prevent any kind of crank case fume pressure to build up and make pressure in the engine.

(valve adjustment)...
Adjusting the valves every 250k miles or so ensures they do not get tighter on the cams. YES, Tighter!. They tighten up because as the engine wears, it is the exhaust and intake valves that wear upwards into the head, causing the clearances of the rockers to the cam to become less and less. Valve seat wear will cause the rockers to ride the cam all the time without clearances, eventually starving them of oil. Some people have even suggested that setting the intake valves to 0.015" instead of the factory 0.014" clearance improves the oil flow to the intake rockers by quite a bit. There are also updated oil pumps (as of early 2019) that provide a bit better oil pressure for the ISX to help this issue too.

(soot and wear metals)...
ANY bypass filter that will remove the bulk of soot in your engine will help stop this problem by leaps and bounds. HOWEVER though, it is NOT RECOMMENDED TO DO EXTENDED OIL CHANGES!. Keep changing your oil like you regularly do and simply use the bypass filter to lower soot and other contaminant levels. Even that el-cheapo Amsoil bypass oil filter that I installed onto my own engine reduced soot levels by 93%. That is a HUGE reduction!.

This certainly explains why some engines have problems with pre-mature overhead cam failures, and the signs are clearly seen simply by removing the top engine cover and taking a look inside. If the rollers for the intake and exhaust rockers are starting to get scared and/or have streaks in them, the top end is sooty-smelling, oil is really black, etc. then this is a sign that something is wrong. Once the rockers start to clog up, then there is only one thing that can be done to reverse this problem. All the rockers and shafts have to be removed, the cross-drillings and passages be cleaned out using brake cleaner and compressed air until none of them are clogged any more.

These 3 main problems (neglect, excess soot or wear metals, and/or excess crank case pressures) also explains why there are so many mechanics that simply claim the ISX gets pre-mature wear in the cams. This also explains why that when people use use bypass oil filters and synthetic oil,.. then not change their oil for 70,000 - 100,000 miles at a time, they get wiped out cams. Suspended wear metals due to lack of flushing out the oil every 15,000 miles builds up in those same small passages and creates deposits that are likely to be worse then the soot.

To me,.. this all makes a lot of sense, and I think it is worth mentioning, so that others can stop this from happening in their engine.


Rocker Oil passages are quite small...
[attachment=890]


When buying a used truck...

- If you are purchasing, or have purchased a used truck,.. It is often the case that these passages are already clogging up and failing. The correct thing to do to save those precocious cams, is to first remove the rockers and shafts, clean out all the passages, inspect everything, re-install them, and perform a proper overhead adjustment. This will ensure that you are at least getting the proper oil flow to the cams and rockers after buying a used engine that has likely been somewhat neglected. Next would be to install a bypass oil filter to get rid of the soot.

Also, if your engine is quite sooty, then you should do your next 3 oil changes at 6,000 - 8,000 miles intervals to help flush the engine of all the deposits.

I don't know about what others are willing to do,.. but I certainly want my engine to last a million miles plus. This problem can be prevented and stopped in its tracks but it takes someone willing to keep after this.

If you have them out...


A rocker shaft cannot withstand more than 0.001-0.002" wear in it before the rockers start starving for oil. It is recommended to replace it if it has 0.002" or more wear in it on inspection to prevent oil pressure drop at the rockers. The rocker bearings are just as important. Before re-installing them, ensure there is less than 0.002" wear in them as well. It does no good to clean everything up if there is too much wear in all the components. The overall oil pressure in the top of the head will drop and everything will be starved of oil if there is a lot of wear.


I have a nice video series on how to replace injectors that explains how to remove and re-install the rockers and shafts. If someone wants to tackle the project themselves,.. I HIGHLY recommend they take lots of pictures of the rockers and shafts BEFORE they disassemble them, so that they can put them back together in the right order.

Here are those videos...
http://rawze.com/forums/showthread.php?t...0#pid16750

And here is the video on doing the overhead adjustment after...

https://youtu.be/gQprOKCVln8


User's Signature: ->: What I post is just my own thoughts and Opinions! --- I AM Full Of S__T!.
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The excess cam wear mystery revealed. - Rawze - 03-05-2016



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