Wear on CAM surface

[bahnburner]

I was doing a valve adjustment when I noticed some wear on the intake CAM lobe on cylinder 6. How bad is this?

This is a '78 3.0L with around 100k miles

[winders]

That's more than normal or abnormal rocker to cam wear.....

That looks to be on the heel of the cam lobe. Is that the case or is that an optical illusion. If it is the heel, it looks more like something got jammed in between the heel of the cam lobe and some part of the cam tower. What does the nose of that cam lobe look like? What does the face of the corresponding rocker look like?

[Classic 911]

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[john walker's workshop]

Never seen wear like that on the heel. Things will need replacing if you do a top end job sometime, but it's a slow growing disease, so no huge worry at the moment.

[winders]

I’m curious as to how that could have happened as the rocker should put zero pressure on the heel of the cam.

[john walker's workshop]

Looks like the lobe to me. There's a heel to the right of it to compare.

[1979-930]

It's the lobe.
I found that same issue on mine. Elgin Cams can regrind the cams and rebuild your rockers.
I would tear down and fix it now. It's winter.

[winders]

Originally Posted by john walker's workshop

Looks like the lobe to me. There's a heel to the right of it to compare.

You mean the nose? Like I said, it could be an illusion as photos are 2D.....if that is wear on the nose, is it smart to keep running it? I know that if the nose of my cam looked like that I would be addressing it as I would not any more metal like that getting in the engine.

[1979-930]

Originally Posted by winders

You mean the nose? Like I said, it could be an illusion as photos are 2D.....if that is wear on the nose, is it smart to keep running it? I know that if the nose of my cam looked like that I would be addressing it as I would not any more metal like that getting in the engine.

Does the exact description even matter with the question asked? The lobe is fuked!

[proporsche]

the whole surface looks very rough..i wonder if the lubrication holes are plugged?
Ivan

[bahnburner]

The wear is leading up to the nose of the lobe. I haven't seen similar damage on any of the other lobes, but I will do a closer inspection. I will have to loosen up the rocker to try and check the underside of it.

I picked up this engine recently as a runner and wasn't planning to do a rebuild... But it seems like more metal could come off the lobe, and worst case the lobe could fail? Neither sound like good outcomes And @1979-930 what is winter?? We don't have that in LA!

[Walt Fricke]

Since the engine is out (right?), remove the rocker shaft so you can get a good look at the rocker face. Pop the oil cooler off if you have a problem getting at the rocker hardware. I can't see running like this, though I well understand grasping at straws. So you will have to do these things and more to get the cam out anyway.

I agree with Ivan that the face of the rest of the cam in your pictures doesn't look right - sort of wavy, Rotate the cam to see if this happens everywhere except on the base circle. And see if other lobes also look like that. That might be a result of very dirty oil? In that regard, how do things look on the left side?

To my eye (I have a dummy cam and carrier unit on my desk at the moment) this looks like it is either on the base circle, or at the start of the transition zone (the ramp). On the right cam the lobes are almost right together, not splayed out like the left cam's lobes are. So the max lobes and the base circles are both at about the same place visually.

But those gouge-like imperfections are not at all like the pitting one sees when the rocker has worn the lobe locally below the surface hardening, or has uncovered a small void in the cam casting.

[bahnburner]

@Walter Fricke thanks for the input. I removed the rocker and took some other pics of the lobes.
I also noticed some wear on the surface hardening of the intake cam lobe on cylinder 4, pretty much on the nose of the cam, not as bad as cyl 6. I took some more as well. The left side looked cleaner and I didn't see similar wear.

Another shot of the intake came on cyl 6. It is in the transition zone.


Intake rocker on cyl 6.



Intake cam on cyl 4.

[mikedsilva]

Time to pull the cams and an opportunity to put something else in there... have your rockers re profiled at the same time too. You have lots of options in the USA for quality work.

[quickxotica]

Here you go:
https://elgincams.com/porsche911/

- Another happy Elgin customer

[1979-930]

Some pics of my valve adjustment that turned into a cam regrind.







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[kyngfish]

Curious how a cam re-grind works. If you remove material doesn’t it necessarily mean less surface area and therefore less movement?

[winders]

Originally Posted by kyngfish

Curious how a cam re-grind works. If you remove material doesn’t it necessarily mean less surface area and therefore less movement?

You weld the lob(s) that needs welding and you regrind the cam.

https://youtu.be/5yINlbAlhlI

[brighton911]

Kyngfish If the re-grind profile chosen is not too radical ( say stock to 964 profile), the base circle of the cam will be reduced equal to the amount removed from the lobes. The smaller base circle is compensated by the valve adjuster screws. And if the profile is a lot different, as Winders stated, hard weld the lobes.

[trond]

Are the two holes in spray bar pointing the wrong direction ?

Another shot of the intake came on cyl 6. It is in the transition zone.