Another piece to the lifter failure mystery

[Zeb]

I drilled and tapped a factory cap, so I’m seeing oil pressure in the filter housing.
The bearings are definitely softer than the roller or the needle bearings.
I think we need to look at this as not simply a pressure issue, but as a pressure/volume issue at the lifter.
Geoff says if you look at the harmonics of a 6.0/6.4 cam lobe on a Cam Doctor, the lobe has a bump on it that shocks the lifter every time it comes around. He likens it to a tire hitting a pothole in the road.
When we think of the lifter getting shocked over, and over, and over again, combined with less than optimal oil pressure/quantity/quality when idled excessively, we get to see the cumalative effect of this.
This is why I think it is primarily a cam issue, but the cam isn’t the only issue.
I think the solution to this problem, for most cases is, Motorcraft lifters, Motorcraft oil filter and cap, and a decent oil, changed at the correct interval.
I tell guys if they’ll do this, they’ll wear the truck out before it needs lifters again!

 

[co04cobra]

I drilled and tapped a factory cap, so I’m seeing oil pressure in the filter housing.
The bearings are definitely softer than the roller or the needle bearings.
I think we need to look at this as not simply a pressure issue, but as a pressure/volume issue at the lifter.
Geoff says if you look at the harmonics of a 6.0/6.4 cam lobe on a Cam Doctor, the lobe has a bump on it that shocks the lifter every time it comes around. He likens it to a tire hitting a pothole in the road.
When we think of the lifter getting shocked over, and over, and over again, combined with less than optimal oil pressure/quantity/quality when idled excessively, we get to see the cumalative effect of this.
This is why I think it is primarily a cam issue, but the cam isn’t the only issue.
I think the solution to this problem, for most cases is, Motorcraft lifters, Motorcraft oil filter and cap, and a decent oil, changed at the correct interval.
I tell guys if they’ll do this, they’ll wear the truck out before it needs lifters again!

I think you are spot on with this.! I see how the cam
Comes into play with it too, but if the guys would run and service them correctly ie: Run ONLY motorcraft filters and IMO synthetic oil. We wouldn’t see but a fraction of the lifter failures.

 

[DEEZUZ]

How does the 7.3 cam profile compare?

 

[Zeb]

How does the 7.3 cam profile compare?

From a durability standpoint it’s fine. He says there are perfomance improvements to be had, but that’s a whole ‘nother subject!

 

[TooManyToys]

Guys, this isn't my normal forum so please excuse my jumping in. I've been curious about this as well and over the past weeks have been trying to research as much as I can. I only have my one motor 6.0 experience but have been looking at as many cam and lifter issues online as I can. BTW, my Ford reman motor is apart but did not have the cam/lifter failure often seen. Never buy a Ford reman ......

I've been trying to look at this from an engineers perspective and there are a good number of papers including those presented within SAE. The preponderance of work is done on the roller cam surface, in some cases stress injury during the grinding process, but other issues related to oil viscosity and debris in the oil. Much of the work revolves around the high pressure of two wheels (lobe and lifter roller) noted under the term Hertzian Contact Stress and when you do the calcs the pressures are very high. Some of the discussion is around the elastic deformation within the two contact points (you can see that by the change in the residual tracking marks) and how over time that can lead to the sub-surface fracturing of the lobe. Throw some debris between the contact point and the loading goes logarithmic under the debris. We see that as pits or brinelling on the ramps or nose of the lobes. Any pitting or brinelling leads to a loss of lubricating film and the stress just gets higher, the stress cracks widen and you can eventually just beat the crap out of the wheel, bearings, and axle of the lifter.

Between the Powerstroke motors, the 7.3L has half the Hertzian contact loading compared to the 6.0L and 6.4L due to the number of valves.

So it can be a lifter issue, but I think it can be a cam issue too. If it is a cyclic fatigue failure, which would be based on cam revolutions, it would occur at the same point with high idle hours, low mileage trucks as with long mileage low idle trucks. It would all depend when/how you get to the revolutions.

Anyway, I'm just throwing that out here but won't drive you insane as I've done elsewhere, I think it's an interesting discussion.

Some info and an image of one of my cam's lobe surface, again no failure, just 75k miles highway. it shows scuffing from the wheel sliding on the opening ramp and the other surface issues. While ramp scuffing is present on all my lobes, the pits or brinelling is all at the last four lobes, cylinders 7 and 8.

Edit- sorry, not familiar with adding images into this forum.

 

[DEEZUZ]

Very awesome posts. Thank you

 

[James W]

Great post A+

 

[TooManyToys]

I worked in R&D my entire career and managed vehicle testing for 35 years, so I can go deep into a rabbit hole where there's no light. And doing that work for so long I've learned there's no absolute answer and hypothesis can be wrong, so don't take this as an absolute.

There were a number of papers I've looked at, some restricted by SAE unless you are willing to pay, but this 20-year-old paper done for a masters degree I think brings home some interesting points. The illustrations work well for cliff notes rather than going through the entire 100 pages.

https://vtechworks.lib.vt.edu/bitstream/handle/10919/36656/etd.pdf?sequence=1

His work is backed up by some other recent work. He touches on the Hertzian contact stress, but anyone can also go on a website to calculate the numbers and there are a number of them. An example,

https://www.amesweb.info/HertzianContact/HertzianContact.aspx

I never gave much thought to the issue before now, but those pressures are up there.

 

[Zeb]

TooManyToys, those are some awesome posts!
The whole thing about a 6.0 cam lobe having at least twice as much load on it as a 7.3 was one of those, “Duh, right!” moments for me. I don’t think that fact ever crossed my mind even tho I knew it!

 

[DEEZUZ]

I've often thought about the dual valve actuation but I kinda leaned towards it was probably equivalent to the single, bigger valve on 7.3

 

[Zeb]

I've often thought about the dual valve actuation but I kinda leaned towards it was probably equivalent to the single, bigger valve on 7.3

Spring pressure would cause more load on the lifter than valve mass, and 7.3’s are notorious for low spring pressure when they are stock.

 

[TooManyToys]

The mass of the pushrod and valve does have an effect, during acceleration of opening and closing, but the open ramp has a higher amount. It does take work to accelerate anything. Using Escobar's graph on the subject with his SVI motor from 20 years ago....





I played around with the values I have between the two different motors, no proofing or review.





On edit, How do you get attachments to load in full size?

 

[DEEZUZ]

Don't even try on this site. I can click them and they expand. Awesome stuff here.


Where did you come from. Lol

 

[Zeb]

The mass of the pushrod and valve does have an effect, during acceleration of opening and closing, but the open ramp has a higher amount. It does take work to accelerate anything. Using Escobar's graph on the subject with his SVI motor from 20 years ago....


View attachment 50395


I played around with the values I have between the two different motors, no proofing or review.


View attachment 50396

On edit, How do you get attachments to load in full size?

It gets fuzzy when I try to get it big enough to read, but what I can make out looks very interesting!

 

[TooManyToys]

It was good that you can't read it as I had to make a correction anyway.

To the chart I added the Hertzian contact pressure. The box to the left are the force values against the cam, but the box to the right is (I hope) the compression between the roller and lobe. It seems to fit in line with Escobar's calculations. I used the site noted at the bottom of the page for the calculations. The contact is so narrow between the two curved surfaces.

One page example from the site.

An image from Escobar's paper showing a side view of a fracture pit, which is why the Depth of Stress is important.

Again, there can be many different reasons why there are the cam/lifter failures, this is just one hypothysis and may be wrong.

 

[DEEZUZ]

That wear pattern is on every single cam I've seen.

But also, the lifter that started this thread was no doubt the cause of the wiped lobe

 

[TooManyToys]

Yep, don't disagree with that.

 

[powerlifter405]

Your better than perfect on the miles vs hours. Trucks been used and put to work.

It's definitely more to do with excessive idle.

Thanks for your thoughts, and you're right it is good to have constructive conversation.

I worked in R&D my entire career and managed vehicle testing for 35 years, so I can go deep into a rabbit hole where there's no light. And doing that work for so long I've learned there's no absolute answer and hypothesis can be wrong, so don't take this as an absolute.

I've read some of your post on the org I believe and seen a few of your yutube vids and especially found the battery cable gauge vs voltage one very useful.
Glad to see you over here :thumbsup:

 

[TooManyToys]

Thanks, Powerlifter. Occasionally at the org, mostly FTE.

 

[powerlifter405]

Thanks, Powerlifter. Occasionally at the org, mostly FTE.

of course and it's great to see guys floating across different forums. It's always good to have some solid discussions vs which vendor sells the highest gigawatt flux capacitor :toast: