What causes this lifter wheel failure?

[turbo camino]

Found this in my 'dead parts' pile, curious what causes it. Sorry, I don't have the cam to see/show what the lobe looks like. Under magnification it's pitted almost like cavitation and it's very consistent all the way around.

Is it... damage in one localized spot that marks up the lobe and from then on the lobe & lifter take turns eating each other? Or just a plain material defect?

[Mikej26]

What did the cam lobe look like?

[turbo camino]

Don't know. I don't even remember if it was from one of mine or something I replaced at work. I've seen this pitting/streaking a few times so I'm sure others smarter than me have seen it too and discovered the root cause.

[Lizardracing]

My first thought would be measuring the wheel and see if it's actually flat and round.
Without the cam, my guess is there is know way of knowing.

[amc fan]

The technical term for this is called "spalling".Fatigue is the result of sheer stresses cyclically applied immediately below the load carrying surfaces.this can be caused by the normal end of the bearings useful life .There are 3 classifications of premature spalling,lubrication,mechanical damage,and material defects. This was taken from an old SKF bearing booklet from the 60's "Bearing Failures and their causes" I hope it helps.

[motionper]

i have seen this on my top fuel harley, i was told it is valve bounce on the seat due to insufficient seat pressure. i upped the open pressure and it seems to have cured it

[turbo camino]

The surface is crowned slightly by about 2.5 tenths in the center, I think that's how it should be. I don't see any wear or anything unusual anywhere outside the streak. Needle rollers & shaft were all in good shape.

This lifter would've come from a stock SBC and judging from the wear on the OD of the lifter body it was rather high mileage, probably high enough that the springs were all used up.

[shoedoos]

^^^^ are you sure about the needle rollers? If those are them in the left of the pic, look at the wear on the couple in on top of the pile....

[turbo camino]

Needles are tapered slightly at both ends so there's some varnish where they weren't contacting their neighbors/axle/wheel ID. There's a matching band of light varnish on the outboard ends of the axle where there was no contact as well. There's nothing other than the damage on the wheel that's out of the ordinary for a lifter at the end of its lifespan.

[turbo camino]

Oh, I see what you saw now - no, the needles aren't necked down in the middle with the ends still fat, that's a camera focus artifact somethingorother.

[turbo camino]

I think this sucker was just worn out and the wheel damage is the natural failure mode. Check out the wear on the thrust side of the lifter body (Dykem & stoned to show the pattern)...

[hoodeng]

amc fan is right, the damage is spalling ,it is when the surface is deformed through load or impact possibly in this case, [motionper's case] the surface is harder through heat treatment [60+-RC] and the core is softer [in comparison] so the core can deflect slightly in response to the surface pressures but the surface can not and deforms, as the surface has no flexibility due to its hardness it cracks off small facets of material till a patch pattern emerges at the point of major deflection and eventually tracks around the full diameter.

I see this at regular intervals in V2 engines where there are stock springs, a bolt in performance cam, a lift in the rev limit, and a heavier right hand.
You can even see instances where there are lines across the bearing surface almost wave like where there is line load/contact perpendicular to the line of rotation.

Cheers.

[turbo camino]

https://www.machinerylubrication.com/Re ... d-bearings

Furthermore, we are firm believers in the “hydraulic propagation theory” that hypothesizes macropitting propagates because oil is trapped in cracks associated with macropitting and pressurized by the rollers. Pressurized oil at tips of cracks causes tensile stresses that advance the cracks. With time, macropitting works its way around the IR. If the bearing is removed from service soon after the macropitting started, surface damage will be evident on only a sector of the IR.

Interesting.

[woody b]

It looks like many lifters I've seen from GM LS engines with "active fuel management". I suspect the lifters bounce when they're de activated. For anyone who hasn't worked on any of these. The lifters are housed in a little plastic retainer. There's a spring that supposed to keep the wheel in contact with the cam when it's unlatched. (not operating the valve). I found this image with an internet search.


The long lifters are the active fuel management lifters. They "latch" closed to keep the valve from moving when the cylinder is deactivated.