5

While I had my valve cover off I noticed that all my cam lobes of this triangular indentation or something:

enter image description here

Anyone know what this is? Is it a feature or a bug? Normal wear?

2
  • What is the year/make/model/engine? This looks line a non-wear area? And which side of the lobe are we looking at? The ramp-up side or the ramp-down side? – Pᴀᴜʟsᴛᴇʀ2 Nov 13 '16 at 12:27
  • @Pᴀᴜʟsᴛᴇʀ2 1998 Mazda 626 2L FS engine – Robert S. Barnes Nov 14 '16 at 7:36
3

tl dr: This appears to be normal wear.

If this is your Mazda 626 2.0L engine, I've pulled up a couple of images of used cams from your type of engine.

enter image description here enter image description here

(NOTE: The images were blown up a bit to show detail and suffer from pixalation.)

In the images, you can see these have the same basic wear pattern as what yours is exhibiting. This, I believe, is a normal wear pattern. What's going on here is, on flat tappet cams, the tappet (or lifter) has to rotate while the engine is running. This ensures there isn't a single wear area on the cam or lifter. In actuality, the tappet base is not exactly flat, but rather is rounded (has a crown in the center). This is what promotes the rotating. If the rotation didn't occur, both the lifter and the cam face would quickly self destruct. The area which is highlighted appears to be on the ramp-down side, where the lifter contacts the cam lobe as the lifter is being allowed to go back to a resting position on the cam base circle. The wear pattern would be due to the spin which occurs as the cam lobe goes around.

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