Cam Lobe Staining
Cam Lobe Staining
A guy is worried about the staining he's found on his cams. Says he cannot feel any marks and they are glass smooth. I't just a couple out of 8 intake lobes. All others, including exhaust are nice and shiny.
Any ideas? Something go wrong with the hardening process or is this possibly nothing to worry about?
Any ideas? Something go wrong with the hardening process or is this possibly nothing to worry about?
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
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- Posts: 1852
- Joined: Tue Dec 06, 2016 4:05 pm
- Location: Elmwood, Wisconsin
Re: Cam Lobe Staining
I think that is the oil additives coating the steel, which is exactly what they are supposed to do. What do the cam followers look like?
Re: Cam Lobe Staining
Most likely it's just not making full contact with the lifter. Not all that unusual, in fact.ctwo wrote: ↑Wed Mar 07, 2018 3:29 pm A guy is worried about the staining he's found on his cams. Says he cannot feel any marks and they are glass smooth. I't just a couple out of 8 intake lobes. All others, including exhaust are nice and shiny.
Any ideas? Something go wrong with the hardening process or is this possibly nothing to worry about?
If hardening was the problem, I expect the cam would be destroyed. If you've ever seen a cam that fails because of hardness issues (either from a lifter or from the cam), I think you'd agree.
H
Wise people talk because they have something to say. Fools talk because they have to say something.
Re: Cam Lobe Staining
Hi There,
high point on the lobe is stained too. This implies that
the lifter/tappet or rocker follower isn't making good
contact with the cam lobe. Normally, the pressure from
the valve spring on the valve train components (at full
lift) should cause the cam follower to wipe with enough
pressure to prevent staining from forming on the high
point of the lobe.
If this is happening only on a couple of lobes, I would look
into the valve train components and the lubrication delivery.
The staining is caused by heat interacting with the oil on
the cam. Some staining is normal but if one area of the
cam shows significantly more staining, this could be an
indication of greater heat build-up in that area. A
significant amount of the heat dissipation for the cam is
through the oil.
Either that, or valve train components don't make any contact
and hence, there isn't any wiping of the lobe and the deposits
are allowed to build-up excessively.
Good Luck!
-Blue Chips-
Webb
Yeah, I've seen that. What is unusual in this case is theHarold_V wrote: If you've ever seen a cam that fails because of hardness issues (either from a lifter or from the cam), I think you'd agree.
high point on the lobe is stained too. This implies that
the lifter/tappet or rocker follower isn't making good
contact with the cam lobe. Normally, the pressure from
the valve spring on the valve train components (at full
lift) should cause the cam follower to wipe with enough
pressure to prevent staining from forming on the high
point of the lobe.
If this is happening only on a couple of lobes, I would look
into the valve train components and the lubrication delivery.
The staining is caused by heat interacting with the oil on
the cam. Some staining is normal but if one area of the
cam shows significantly more staining, this could be an
indication of greater heat build-up in that area. A
significant amount of the heat dissipation for the cam is
through the oil.
Either that, or valve train components don't make any contact
and hence, there isn't any wiping of the lobe and the deposits
are allowed to build-up excessively.
Good Luck!
-Blue Chips-
Webb
-
- Posts: 1852
- Joined: Tue Dec 06, 2016 4:05 pm
- Location: Elmwood, Wisconsin
Re: Cam Lobe Staining
If the staining was due to the cam follower was making intermittent contact the high spots would be shiny and the low ones stained. If it was making no contact at all surely the machine would fail to run properly. Thus if the cam is uniformly stained and the valve operates correctly the cam follower is probably maintaining uniform light contact. Isn't that what you want?
Re: Cam Lobe Staining
Hi There,
valve, it compresses a spring. As the spring is compressed,
the pressure on the valve train goes up. Therefore, it isn't
uniform by design.
Good Luck!
-Blue Chips-
Webb
But, that isn't how it works. As the valve train opens theJohn Hasler wrote: ↑Thu Mar 08, 2018 5:14 pm Thus if the cam is uniformly stained and the valve operates correctly the cam follower is probably maintaining uniform light contact. Isn't that what you want?
valve, it compresses a spring. As the spring is compressed,
the pressure on the valve train goes up. Therefore, it isn't
uniform by design.
Good Luck!
-Blue Chips-
Webb
-
- Posts: 1852
- Joined: Tue Dec 06, 2016 4:05 pm
- Location: Elmwood, Wisconsin
Re: Cam Lobe Staining
Ok, continuous. The point is that if the cam follower is always touching the cam it is doing its job.
Re: Cam Lobe Staining
There is supposed to be a point where the valve doesn't touch the cam lobe. I think the cam is fine but would agree there could be an oiling issue around there.
This is an early valve check so wear may not generally be observable at this interval.
Thanks
This is an early valve check so wear may not generally be observable at this interval.
Thanks
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
Re: Cam Lobe Staining
Only if the engine in question has mechanical lifters. Hydraulic lifters maintain constant contact, albeit at light pressure.
I don't think there's an oiling issue. If there was, it would manifest itself by destroying the lobe and follower/lifter. Note that there's an almost perfectly shiny area on the right hand side in the picture provided. That indicates, to me, that there is contact, but that the lobe on the cam is not ground parallel to the surface making contact, although very close. I believe that's the reason for the discoloration.I think the cam is fine but would agree there could be an oiling issue around there.
I fully expect that if oiling was a problem, the area that displays shiny would show signs of gulling. Take a look at the mating surface to see if there's signs of wear, although I expect there isn't. If it's a lifter, and it's spinning properly as it operates, I expect you'll find the center slightly discolored, while the outer edge will be polished from contact with the lobe.This is an early valve check so wear may not generally be observable at this interval.
I could be wrong.
H
Wise people talk because they have something to say. Fools talk because they have to say something.
Re: Cam Lobe Staining
H. You could be wrong but I don't think you are. The pattern is repeated upon the next shown cam lobe. We don't even know what engine this is.
Re: Cam Lobe Staining
This is overhead cam and there is likely a shim and bucket sitting on top of the valve. The owner is panicking over finding new cams or getting these reground. I suggested he just rub them with some scotch brite and reinstall them, and check them a bit early on the next check. I was just interested in the color pattern on the lobes. It reminds me of my Lufkin height gauge base.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
Re: Cam Lobe Staining
There is the fact that some engines had hydraulic lifters/ cam followers With mechanical adjustment to final clearance. It is possible that these were inserted upside down so that the adjustments were more easily done under the cam covers.