Another Cam bites the dust...

[ShadowsPapa]

I agree, this seems to be a common problem. Why so many cases where the failure occurs on the intake cam, right back, on cylinder number one? At least that is what I find in my research. At 7900 miles, it is difficult to blame owner behavior, oil, break-in etc. If this was just a materials problem, I would expect failures to be spread throughout the valve train, both intake and exhaust. Something is off.

It's been a mix of cylinders on the right bank, and a few on the left. We've seen 3 and 2 go as well if you look at the photos.

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[OldButStillJeeping]

There is literally nothing to match. Journal clearances. And it has nothing to do with who owned who or what.
The journal clearances have a range, and being at either edge of the range will have zip to do with cam life or operation. Nothing.
I wonder if sometimes techs do things becaus because that's what they are told, that is what the factory says, or some other reason - even if there is really no sound logic or science behind it.
If the journal fit is snug, as long as it's in specs, it means little.
If it's on the looser side but in specs, it only means potentially shorter cam bearing area life - maybe, but generally not because there's so much control over the oil system. The pressure is regulated. So if the journals weep out a tad more oil than a tighter fit - no biggy, you just get more volume through but the system still all gets the same oil it should, the same amounts and pressures.

My challenge to them would be to put one of those heads on my bench and check the cam bearing area/journal clearances. Check cam runout.
Now, swap cam only, and then tell me if it's out of spec, or why it's not going to work. Show me the proof it's "necessary" instead of "that's what we're supposed to do".
I have all of the tools here for measuring - inside and outside micrometers of all sizes 0 to 5", a pair of stands used to check for balance and runout, dial indicators from Kent-Moore and Starrette, plastigauge in various sizes uses to check clearances on shafts with removable bearing caps and more.

You know more than I.

I think it has more to do with collateral damage to the bearing surface on the head when a cam goes south. And other collateral damage to everything in the valve train. Some things are unseen. Can't be measured while under stress in operation.

On engines that cost more than a brand new complete JT Sport, nothing is left to chance.

But that is my take on it.

And, again, you know more than I. I respect that.

 

[OldButStillJeeping]

You have to get WAY up there in RPM and even then, not really. High RPM high performance engines doing 7,000 or so RPM - they swap cams without issue.
For being really picky, I have a cam bearing hone that will hone a perfectly straight path through the bearings and to the size needed.
If there are no cam bearings - if it just rides on the aluminum head, then you might have some wear there - and can't just replace cam bearings to compensate like a V8. OHC engines running just on the head aluminum with no special bearing, they might be talking WEAR on head, not a "custom pair".

Racers and wanna be, swap cams w/o issue to change the cams lobe angle for performance, not as a repair for a bad cam. Well, maybe they do.

I did it a long time ago. As a wanna be. Get more performance...

But a bad cam in a factory engine repair? A warranty repair? What else was damaged?

Could simply be the metallurgy of the alum head is compromised from the contractor that built them.

If my JT has this cam issue. I will replace the whole head and that side valve train. My JT is out of warranty at over 60K miles anyway.

 

[ShadowsPapa]

Racers and wanna be, swap cams w/o issue to change the cams lobe angle for performance, not as a repair for a bad cam.

I did it a long time ago. As a wanna be. Get more performance...

But a bad cam in a factory engine repair? A warranty repair? What else was damaged?

And my last engine builds and repairs and valve train work was - let's see, oh, just a couple of years ago in my shop.

Uh, I sort of know all about that........ just a little bit LOL.
What else is damaged? Nothing. Not with a bad lobe and follower (or in the V8 - the lifters)
It doesn't wipe out anything else. The bearing surfaces, if fine before, are fine after. A bad lobe doesn't increase wear elsewhere. If anything, it reduces the load as it can't push the valve spring as tightly collapsed so there's LESS force against it, not more.

I've worked in shops for years and do my own engine builds these days - I know what is and isn't worn in the case of a bad lobe. It's zero wear to anything else.
There's nothing about a lobe and follower that will wear or ruin bearings or change clearances and there's nothing about a loose bearing that will impact lobe or lifter life.
Nothing else is damaged.
It's one reason that most auto makers will simply supply the cam and related parts - and say "fix it". Because there's no relationship to anything else at all.
So you can swap cams like the big boys do on the track - just swap the cam and followers and be done with it.

I'd love to see someone explain how a bad lobe damages a head or other parts unrelated to the valve train itself - I'll wait.

 

[OldButStillJeeping]

And my last engine builds and repairs and valve train work was - let's see, oh, just a couple of years ago in my shop.

Uh, I sort of know all about that........ just a little bit LOL.
What else is damaged? Nothing. Not with a bad lobe and follower (or in the V8 - the lifters)
It doesn't wipe out anything else. The bearing surfaces, if fine before, are fine after. A bad lobe doesn't increase wear elsewhere. If anything, it reduces the load as it can't push the valve spring as tightly collapsed so there's LESS force against it, not more.

I've worked in shops for years and do my own engine builds these days - I know what is and isn't worn in the case of a bad lobe. It's zero wear to anything else.
There's nothing about a lobe and follower that will wear or ruin bearings or change clearances and there's nothing about a loose bearing that will impact lobe or lifter life.
Nothing else is damaged.
It's one reason that most auto makers will simply supply the cam and related parts - and say "fix it". Because there's no relationship to anything else at all.
So you can swap cams like the big boys do on the track - just swap the cam and followers and be done with it.

I'd love to see someone explain how a bad lobe damages a head or other parts unrelated to the valve train itself - I'll wait.

You win.

I will shut up now.

Thank you Sir

 

[MPMB]

I expected the same from a modern 3.6 because Mercedes owned Jeep for awile. Some good things came from that merger for Jeep.

Fun fact: One of the driving reasons MB pursued the merger was to capitalize on American auto production techniques.

When they finally got the hands of the "proprietary" financial info, the bigwigs at MB saw the cost Chrysler spent to produce an "entry level" sedan, probably the Sebring or optimistically, the 300M. It was slightly cheaper than the cost MB incurred in producing their E-class sedans, which sold for thousands more than either of the other two.

For reference, the 1999 300M retailed for $28k+, whereas the '99 MB E-Class started at $42k. Moving to today, the final 300C version had an MSRP of $56.6k and today's E-Class starts at $62k. If you want something with power to match the 300C, you're going to need the AMG version at $88k or give up some ponies with the $71k E450 with a turbo-6 at 375hp.

 

[ShadowsPapa]

LOL - that wasn't the point to win or lose - the point is - show everyone here how there's going to be other damage. And - how Jeep has been wrong for several decades when talking about cam replacement - heck, for that matter, GM, Ford and others.
Otherwise people who do searches will freak out and say OMG! Jeep screwed up my engine! I demand a new head, too!

Why?

Unless you plug the filter and it goes into bypass mode - maybe due to thicker oil or contamination from damage, filtered oil reaches all bearing journals. Now - pull the caps, look for scoring - none? Good, the filter didn't go into bypass, oil was filtered.
Replace cam, followers, change the oil, then change it again after a shorter than normal interval. Life is good.
You will witness any other damage while taking it apart to swap the cam.

Fun fact: One of the driving reasons MB pursued the merger was to capitalize on American auto production techniques.

When they finally got the hands of the "proprietary" financial info, the bigwigs at MB saw the cost Chrysler spent to produce an "entry level" sedan, probably the Sebring or optimistically, the 300M. It was slightly cheaper than the cost MB incurred in producing their E-class sedans, which sold for thousands more than either of the other two.

For reference, the 1999 300M retailed for $28k+, whereas the '99 MB E-Class started at $42k. Moving to today, the final 300C version had an MSRP of $56.6k and today's E-Class starts at $62k. If you want something with power to match the 300C, you're going to need the AMG version at $88k or give up some ponies with the $71k E450 with a turbo-6 at 375hp.

Yeah, and market reach. Funny thing, MB learned from Chrysler as well as the other way around.

I compared a Grand Cherokee we owned with a friend's Mercedes (he was one of their top techs at a Germantown location near DC)
It was quite interesting, our conversations and comparisons of certain automotive things.
What made us both laugh was comparing key fobs. ZERO difference except the Merceders fob had a chromed edge.

 

[MPMB]

I'd love to see someone explain how a bad lobe damages a head or other parts unrelated to the valve train itself - I'll wait.

Our only "catastrophic" engine failure in my ~16 years racing was our Katech (name drop! :D) engine was way, way, beyond it's serviceable life. 2500 laps on it before the season started. Set the track record with it, and after inspection, it only pumped 8.9:1 compression ratio instead of the 9.5:1 limit. Huh.

A needle bearing eeked out of the cam and went through the motor, eventually getting jammed between the external 4 stage oil pump' gears. That killed the oil pressure.

 

[smlobx]

….It's been a very very long time since there was any "break-in oil" put in from the factory. Last time was probably before half the members here were born.
I try to go 2-3K on the first and no more.
And that includes the engines I build myself.
I put in what I'm going to run, make the first change interval short (ring wear-in materials, other things that need to be flushed out) and go from there. Nothing special.

Well Bill he’s older than both of us so I can believe they used break ins oil back in the day…particularly high performance engines.

On Another note, one day I asked him what vehicles they used to get real world data from and he told me that they work out a deal with the major taxi companies in New York, Chicago etc. and when they buy new taxis ( 500 a year or so) they have the taxi companies do a strict oil change schedule with their oils and after something like 100k to 200k they pull the engines and put new engines back in for the taxi companies. It’s a win/win because the taxis are run almost 24/7 in the worst stop and go driving.

 

[JTGuy]

Our 3.6 isa mass produced engine. There is nothing hand built about it. The cam failure is designed into it, not caused by assembly. It will go till it fails, and it will eventually will fail. My plan is to dump this dog before it does fail. That will be just luck, or not. Or I could just save the money lost in it and just fix it. With the HP and RPM we are running it takes very little to cause a failure over time and miles.

 

[ShadowsPapa]

Our 3.6 isa mass produced engine. There is nothing hand built about it. The cam failure is designed into it, not caused by assembly. It will go till it fails, and it will eventually will fail. My plan is to dump this dog before it does fail. That will be just luck, or not. Or I could just save the money lost in it and just fix it. With the HP and RPM we are running it takes very little to cause a failure over time and miles.

So, you believe mass produced engines aren't put together pretty much 100% by HUMANS? And that an individual person working a shift can't mess something up? Think again.......

Humans pretty much every step of the way, from installing pistons, rods, cam shafts, timing chains, phasers, name a part, a human probably put it in place and tightened the fasteners.
And with mass produced sometimes comes mass mistakes. (just ask GM!)

 

[AdamC149]

If anyone could send me a bad cam, I will do a metallurgical analysis on it. It's my current opinion that the issue with the cams are a material / process flaw.

 

[JTGuy]

People assemble them only because a robot doesn't, yet. Nothing the person does determines the non failure of the cams that we are having. The parts are all the same and are not custom fitted into each block. If your cam fails there is nothing special about its replacement and nothing special is done when installing it to prevent it from failing just like the original one did. The have no way at this time to prevent it from happening again. If there was they could prevent the first failure. .

 

[ShadowsPapa]

People assemble them only because a robot doesn't, yet. Nothing the person does determines the non failure of the cams that we are having. The parts are all the same and are not custom fitted into each block. If your cam fails there is nothing special about its replacement and nothing special is done when installing it to prevent it from failing just like the original one did. The have no way at this time to prevent it from happening again. If there was they could prevent the first failure. .

Ya think I don't realize and understand all of that.
There have been some issues found with oil passages, galleries, according to some. But mostly, it's a materials or process issue.
On the other hand - there are some variations in manufacturing that cause some parts to be labeled for other fitment - it's a real thing. They allow for that and if you've worked on enough engines, you've seen the stampings or marks or codes on them.

That video doesn't show all steps, all processes involving people and inspection points, but it's very possible that a small number of issues, perhaps on the left side, are attributable to human error or missed inspections. (my father was head inspector in a factory - if he was alive - the stories he could tell..........)

We don't know the supplier of the cams - or where the left comes from if it's the same supplier as the right and so on. There are many unknowns.
Out of every 5,000 that have gone bad - I'm betting that at least a handful are "other causes". I'd bet on it.
We have to somehow explain why just a few left side cams go vs. the right side, why some go hundreds of thousands of miles with no issues while others go 1,000 miles and have trouble.
But any time and item fails, it's always assumed it's the SAME cause in every case. We don't know that, we can't know that.

 

[Bigcatfish]

Our 3.6 isa mass produced engine. There is nothing hand built about it. The cam failure is designed into it, not caused by assembly. It will go till it fails, and it will eventually will fail. My plan is to dump this dog before it does fail. That will be just luck, or not. Or I could just save the money lost in it and just fix it. With the HP and RPM we are running it takes very little to cause a failure over time and miles.

Yall are making me nervous. I bought a new gladiator 3 weeks ago.

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