Cam-follower facings' phenomena

[e3steve]

A question, to start the ball rolling and to seek experience from the forum's vast knowledge base:

I have two types of valve rocker to work with upon motor rebuilding; the pic speaks for itself, but I'm a little bemused by the fact that the later-and-supposedly-better of the two different oiler systems appears to have suffered accelerated wear patterns.

Can these be re-faced? Or is the hardening too thin on the follower face?

And, more importantly, do I use the later type at all?! These both came from the same motor, apparently.

I've tweaked the mid-tones on the second pic to accentuate the wear pattern.

Thanks for any input, people.

[LOUD MOUSE]

That part is the last design (810) and yours isn't the first I've seen with wear.
Sure do wonder what went on over the years.
Hows the cam lobe? (BAD!)
I don't think ya can repair them for near the cost to just replace them. ..................lm

A question, to start the ball rolling and to seek experience from the forum's vast knowledge base:

I have two types of valve rocker to work with upon motor rebuilding; the pic speaks for itself, but I'm a little bemused by the fact that the later-and-supposedly-better of the two different oiler systems appears to have suffered accelerated wear patterns.

Can these be re-faced? Or is the hardening too thin on the follower face?

And, more importantly, do I use the later type at all?! These both came from the same motor, apparently.

I've tweaked the mid-tones on the second pic to accentuate the wear pattern.

Thanks for any input, people.

[teazer]

That is common, in my experience. It's not wear as such, but it's a phenomenon known as brinelling. In this case, the rocker material under that hard chrome plating has indented (collapsed). If you removed the plating, the underlying material would still show the same pattern.

Older styles had a tendency to scuff and wiped the plating off along with the cam surface. The idea was to make sure that the oil creates a wedge on which the cam and follower would ride to prevent metal to metal contact.

The best solution is to get someone like MEGACYCLE cams reface the rockers arms. That creates a thick enough layer of hard weld to prevent the pad from collapsing.

I went through several sets of rocker arms recently and most of the early types were scuffed and worn and probably half the later ones were collapsed. Your experience may differ.

[LOUD MOUSE]

Collapsed?
Are ya saying the area at that hole is hollow?. .......lm

That is common, in my experience. It's not wear as such, but it's a phenomenon known as brinelling. In this case, the rocker material under that hard chrome plating has indented (collapsed). If you removed the plating, the underlying material would still show the same pattern.

Older styles had a tendency to scuff and wiped the plating off along with the cam surface. The idea was to make sure that the oil creates a wedge on which the cam and follower would ride to prevent metal to metal contact.

The best solution is to get someone like MEGACYCLE cams reface the rockers arms. That creates a thick enough layer of hard weld to prevent the pad from collapsing.

I went through several sets of rocker arms recently and most of the early types were scuffed and worn and probably half the later ones were collapsed. Your experience may differ.

[MBellRacing]

I've heard of this sort of thing on other surfaces. The very hard top surface has a very established and tight structure but the underlying material is relatively loosely structured and is more prone to "collapsing". There's no air bubble or something like you imply, I think the comment was more to say that the surface itself isn't the only thing holding a change in shape.

[LOUD MOUSE]

Help me with this.
The cam lob and face of the follower BANG/RUB each other and are ya saying the metal doesn't wear away it collapses?. ..........lm

I've heard of this sort of thing on other surfaces. The very hard top surface has a very established and tight structure but the underlying material is relatively loosely structured and is more prone to "collapsing". There's no air bubble or something like you imply, I think the comment was more to say that the surface itself isn't the only thing holding a change in shape.

[teazer]

Correct. Imagine a harness tester. You know the way that it leaves a dent in the material. Well this is similar. The steel under teh plating becomes more compact if you will. Collapses sounds a little dramatic, but the structure collapses and allows the molecules to pack tighter together.

Keep in mind that spaces between molecules and spaces between sub atomic particles are much larger than the particles themselves. A SOLID material is only solid relative to other objects.

Think of a black hole. The atoms and sub atomic particles are so close together that a object the size of the world can fit on teh head of a pin - more or less)

We are not talking anything that dramatic here, but the principle is similar.

If you strip of the few thousandths of hard chrome plating, the material underneath is still "collapsed". freaky eh.

That's one of the ways that gears fail. All those "wear" marks are usually the same phenomenon. The material under the hardened shell collapses in. The surface of a gear tooth with that sort of issue still has more or less the same thickness of case hardening - it's the softer core that is collapsing.