The excess cam wear mystery revealed.

[Rawze]

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...




Rocker shafts starved of oil...



And then the cams themselves get starved of oil too.



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...


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

[386lover]

This is what my injector cam looked like a year ago right after I bought my truck. I'm glad I decided to do an overhead right away.

[Magard]

.002 of an inch wear wow. Way to go big red. Is there something to do to the block during a rebuild that would feed more oil to the cams. I've read the dime shims in oil pump bypass spring. Basically I'm asking if the cross drillings need to be opended up somewhere or is there something that needs to be tapped and plugged. This problem reminds me of Cleveland blocks and oiling issues especially after a little wear. It's a old hot rod thing. Major design flaw fixed buy drilling and taping and plugging a oil galley that wasn't really needed.

[Rawze]

(03-13-2017 )Magard Wrote:  .002 of an inch wear wow. Way to go big red. Is there something to do to the block during a rebuild that would feed more oil to the cams. I've read the dime shims in oil pump bypass spring. Basically I'm asking if the cross drillings need to be opended up somewhere or is there something that needs to be tapped and plugged. This problem reminds me of Cleveland blocks and oiling issues especially after a little wear. It's a old hot rod thing. Major design flaw fixed buy drilling and taping and plugging a oil galley that wasn't really needed.

Shimming the pump with 6-8 dimes makes a huge difference in flow to the top end. It is looking like 6 dimes for the CM2250 and 2350's (only one cam up there), and 8 dimes for the CM870 and 871's does the trick nicely without getting too crazy.

The most effective solution is to ensure the oil stays clean and does not get too much wear metals built up in it. - I.E. changing the oil often, even if you use a bypass filter.

[sirrepairsalot]

I got an engine waiting outside the shop for this service of broken/worn rollers and cams... I just did the overhead set awhile ago too, checked for loose components didn't find none. Guess it was too late for reversal... It's worn right out this engine, but the company dont want to spend the money to repair it properly.. Hard to tell em it's their fault cause they are cheap... Diesel flush with an overhead set would work wonders too I'd imagine.

[Rawze]

(10-26-2017 )sirrepairsalot Wrote:  I got an engine waiting outside the shop for this service of broken/worn rollers and cams... I just did the overhead set awhile ago too, checked for loose components didn't find none. Guess it was too late for reversal... It's worn right out this engine, but the company dont want to spend the money to repair it properly.. Hard to tell em it's their fault cause they are cheap... Diesel flush with an overhead set would work wonders too I'd imagine.

Thats sad.

In the video series I made back in april-2016 for my engine rebuild, I only replaced the back 3 injectors. The engine had 950,000 miles on it. Cams looked great.

I just replaced the other 3 this week (the front 3), and gave a really good inspection of the top end, cams now have 1.16 million miles on them. BOTH the overhead cams are still looking good and there is no signs of needing replacing yet, but I did notice that the polishing on the cam lobes has completely changed. I would suspect that this is because of the new head. Other than that, It all still looks good.

-- Sorry, but I am a believer in doing what actually works instead of taking the advice from people who have repeating failures.

People who have repeating failures tend to do one or more of these things ...

* Do extended oil changes and/or use synthetic oils.

* and/or don't change their oil often enough, then soot takes its toll.

* and/or Use all sorts of hokey fuel or oil additives.

* and/or Turn their power up above 500 HP mostly because they don't want to be the last guy up the hill, or they are too damn lazy to shift gears when necessary.

* and/or Don't keep their engine and emissions systems in good health, yet most who neglect the hell out of their engines will go out of their way to polish the hell out of that chrome on the outside of their truck. How ironic is that eh?

* and/or Drive fast and run their engine hard, yet only complain about it when something breaks. They tend to also not have any money to fix anything major because they drove it like a madman fool, wasting all their profits on bad driving habits.

* and/or have this mentality of trying desperately save 10 cents here and there by extending their oil change intervals, nickeling the hell out of everything they can all while it costs them 2-3x more money while everything on the truck falls apart. There are a ton of guys who fall into this category. I see their beat up equipment all over the roads these days. -> I see re-caps on the drives, shocks rusted out and bad, cracked fenders, worn to the bone steer tires, engine oil smells like the inside of a fireplace it has so mush soot buildup, neglected air, power steering, and water filters, after-market crap hanging off the side of the engine, exposed wiring from that failed lighting experiment or that roadside repair that never got fixed properly, rusted out mud flap holders, cab mounts and other bushings beat to snot, and the shifter so loose from abuse that it feels like someone used it in a row-boat contest. I could keep going. lol

[obsawyer]

Thankx for all the great Reading here! I learn more and more every post!! Awesome!!

[multitask]

(03-13-2017 )Rawze Wrote:  

(03-13-2017 )Magard Wrote:  .002 of an inch wear wow. Way to go big red. Is there something to do to the block during a rebuild that would feed more oil to the cams. I've read the dime shims in oil pump bypass spring. Basically I'm asking if the cross drillings need to be opended up somewhere or is there something that needs to be tapped and plugged. This problem reminds me of Cleveland blocks and oiling issues especially after a little wear. It's a old hot rod thing. Major design flaw fixed buy drilling and taping and plugging a oil galley that wasn't really needed.

Shimming the pump with 6-8 dimes makes a huge difference in flow to the top end. It is looking like 6 dimes for the CM2250 and 2350's (only one cam up there), and 8 dimes for the CM870 and 871's does the trick nicely without getting too crazy.

The most effective solution is to ensure the oil stays clean and does not get too much wear metals built up in it. - I.E. changing the oil often, even if you use a bypass filter.

Hey Rawze, can I use stainless washers instead of dimes? We don’t have any coins here of that size. Thanks

[Rawze]

(03-08-2018 )multitask Wrote:  Shimming the pump with 6-8 dimes makes a huge difference in flow to the top end. It is looking like 6 dimes for the CM2250 and 2350's (only one cam up there), and 8 dimes for the CM870 and 871's does the trick nicely without getting too crazy.

The most effective solution is to ensure the oil stays clean and does not get too much wear metals built up in it. - I.E. changing the oil often, even if you use a bypass filter.

Hey Rawze, can I use stainless washers instead of dimes? We don’t have any coins here of that size. Thanks
[/quote]

Should work fine. Just make sure you have the correct total thickness and diameter.