Cam Lobe Staining

[warmstrong1955]

I've seen markings like that, more often with solid lifters, but also with bad or weak hydraulic ones. They can get to 'slapping' the cam lobes when there is too much clearance.
Lack of oil, or the wrong oil will do that too....but usually not just limited to two lobes.
Stuck or sticky rollers will do it too, but that is obvious on the roller.
What do the lifters look like?
A lack of hardening....which I have seen with solid, hydraulic, and rollers....is obvious and can get ugly, especially if there is or are excessive clearances, and worsens rapidly as the gap gets larger on its own.
Last engines I remember repairing that had a factory hardening problem, was some Isuzu 6RB1T's in Hitachi excavators. (300 HP diesel) The cam lobe, they missed hardening one, was no longer a lobe, but round, in 1000 to 2000 hours.

Looking at the pic....I would do the same as you suggested, and polish up the lobes a bit and run it. Doesn't look bad to me at all.

Bill

[wlw-19958]

Hi There,

The "splotchy" appearance of the lobe kind of
looks like rust (it probably isn't but it has that
"look").

I figured this was an overhead cam set-up. The
base looks like aluminum. If it is the kind of set-
up I'm used to, it will have rockers that have a
follower on one end and an adjustment screw with
lock nut on the other (for adjusting valve lash).
This is a mechanical valve train and it will have
zero pressure on the heel of the cam lobe.

...the area that displays shiny would show signs of gulling.

I surely hope you meant "galling" (look up "gulling"
and the slang interpretation and you'll know what
I mean).

I just don't quite fathom why there is staining on the
high point of the cam lobe (if the valve train is working
properly). That point should be under a lot of pressure
and would prevent staining from occurring.

If your friend is worried about the cam, check the lift
of the lobes and compare them to specs and the other
lobes that are not stained.

Good Luck!
-Blue Chips-
Webb


Good Luck!
Blue Chips-
Webb

[Harold_V]

...the area that displays shiny would show signs of gulling.

I surely hope you meant "galling" (look up "gulling"
and the slang interpretation and you'll know what
I mean).

Sigh! Yeah, that's what I meant. It's not the first time I've used that word the wrong way. Seems to be some kind of mental cramp. Or, maybe, old age! (I already knew the difference-but that didn't seem to stop me from using the wrong word.)
Thanks for the correction.

H

[spro]

I think Bill has it right about hydraulic lifters failing. In my experience, the way the engine comes to rest, creates valve train noise. There is excessive gap until everything warms up. It is only one or two but sounds like a gap of .038 ( compared to the rest of the engine)
What this may be seen to the camshaft lobe is a hammering. The lifter is failing because it was under compression when the engine shut down.
This engine is an EJ Subaru with mechanical adjustment over hydraulic lifters. When one fails they are All replaced.

[jpfalt]

It could well be an area with low lubrication. Those surfaces will run hotter and varnish out the oil on the metal surface. You didn't mention if he was running a non-detergent oil as this will lead to additional varnish buildup.