Engine Ticking Sound

[Renegade]

Poor maintenance ->

Contrary to what people claim on the web out there, engines exist that aren't strictly roller type valve trains. These experience forces, frictions, similar to the "old flat tappet" engines of the last century.
That means maintenance is important, and the same things that caused issues in the past can cause issues today - manufacturing issues, materials not properly treated - nitriding, carburizing, induction hardening.............
Not sure what these would go through without digging, but is it the follower or rocker, or the cam itself? At least the old school cam design saw the lifters constantly rotating, these simply drag across the cam lobe (well, unless riding the rollers on the edge lobes)

One company has shown that your old school roller lifters with bearings were problematic so they went to a bushing type system. Too much concentrated force on the roller bearing needles.

The needle bearings in the roller fail, and the rocker itself contacts the cam.

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[ShadowsPapa]

Then perhaps time to get rid of the needle bearings. That's what happened years ago in the roller lifters for AMC engines (for racing and high performance builds). The needle bearings can't handle the stress due to the tiny point of contact. When you lower the "square area" of contact using the same pressure, you increase the force on that area. They got rid of the bearing and went to a bushing type of bearing.
We've all seen how the needle bearings can cut into the cross on a u-joint but those are in a more constant contact. These are relaxed, then smacked, then relaxed, then smacked.
At least that's my theory - and it aligns with the removal of "bearings" from roller lifters years ago.

This is from one site discussing the pros and cons of bushings vs. bearings. There's still a good side to bearings and they work. Not everyone is moving to bushings, some companies offer both and some builders request bearings rather than bushings, but -

If you refer to the sidebar reference from the Bosch Automotive Handbook, you’ll see that one of the disadvantages of needle bearings is they are highly susceptible to impact loads. The result of these hammer-like loads can be a tiny indentation in one of the needle bearings. When this occurs, the needle will stop spinning and begin to slide. When this occurs, it creates unwanted friction, and will soon fail.