Intake rocker? cam lobe wear opinions

[mike sampsel]

Is this cam lobe wear normal?

[pampadori]

I can't tell for sure but It is on the part of the lobe that is pushing down on the rocker arm or is it on the "dead" part that has a valve lash gap between it and the rocker arm? Might not be a big deal at all it is on the dead part.

Mine had some pitting there too and that was what I was told.

[proporsche]

i would say you need new cams..They are not expensive for SC.
I would not used them definitively.

Or send it out to be regrinded....

Ivan

[john walker's workshop]

But it is unfortunately pretty normal. General feeling is due to insufficient zinc and phosphorus in the oil choice. Use something like PennGrade 20/50. Yeah, new cams. Don't care for regrinds, personally. Webcam 20/21 grind perks up a 3.0 nicely.

[mike sampsel]

Thank you gents,

Sweet I can use these cams for yard art!
Bummer, all my care to ensure I got my rockers ordered correctly is for naught

[HarryD]

Originally Posted by mike sampsel

Thank you gents,

Sweet I can use these cams for yard art!
Bummer, all my care to ensure I got my rockers ordered correctly is for naught

Sorry to hear. For the record, what oil brand/weight have you been using?

[mike sampsel]

Let’s see: mostly mobile one 15/50. Last two changes were VR1 20/50.
Of course the high zinc is hard on the catalytic converter IRC.

[HarryD]

Originally Posted by mike sampsel

Let’s see: mostly mobile one 15/50. Last two changes were VR1 20/50.
Of course the high zinc is hard on the catalytic converter IRC.

Good oils. Hopefully not the source of your woes.

[Peter M]

It's a pretty long bow to blame the oil. It's certainly not something that occurs during the last couple of oil changes. Poor heat treatment is a more likely cause. Also if you Google "Lycoming camshaft spalling" you'll likely see a whole lot of lobe damage initiated by corrosion pitting.

From what I can figure out regular long runs to keep the oil in good condition and corrosion at bay and ZDDP around the 1100ppm seems to be the prudent approach (However getting statistical evidence to support that is impossible and have to rely on anecdotal evidence from people that work on these cars everyday)

My bet however is that the reality is there is nothing the owner could have done differently to prevent that spalling.

[HarryD]

Originally Posted by Peter M

It's a pretty long bow to blame the oil. It's certainly not something that occurs during the last couple of oil changes. Poor heat treatment is a more likely cause. Also if you Google "Lycoming camshaft spalling" you'll likely see a whole lot of lobe damage initiated by corrosion pitting.

From what I can figure out regular long runs to keep the oil in good condition and corrosion at bay and ZDDP around the 1100ppm seems to be the prudent approach (However getting statistical evidence to support that is impossible and have to rely on anecdotal evidence from people that work on these cars everyday)

My bet however is that the reality is there is nothing the owner could have done differently to prevent that spalling.

You are probably correct. When I had the top end on my 160,000 miles there was mild pitting on my lobes. They were polished and all seems ok. I have been using Brad Penn 20W-50 since I got the car in 2003.

[pmax]

Agree on not drawing any conclusions from one sample point (statistically speaking). However, length of usage and oil change intervals would be important to note as well "for the record".

[T77911S]

take a look at the spray bar.
you could have had a clog in one of the holes.

[safe]

Originally Posted by pmax

Agree on not drawing any conclusions from one sample point (statistically speaking). However, length of usage and oil change intervals would be important to note as well "for the record".

I'm pretty sure John W has more data points than this cam....

Pitted cams was never an issue before the zink and phosphorus content was lowered.
I've spoken to lots of old timers that has never heard of these problems back when these cars wasn't outdated.

[db_cooper]

Originally Posted by safe

I'm pretty sure John W has more data points than this cam....

Pitted cams was never an issue before the zink and phosphorus content was lowered.
I've spoken to lots of old timers that has never heard of these problems back when these cars wasn't outdated.

Although I might resist the label of being an "old timer" I must disagree. Back in the day we saw camshafts worn exactly like that. The "hardening" layer on the camshafts is wearing off. Those are not "pits".

It is too easy to blame a lack of "zinc" in the oil and ignore a questionable service history or incompetents working on the car .

Usually wear on a couple of lobes is/was a poor valve adjustment, or infrequent valve adjustments. Too tight or too loose will cause individual cam lobe/ramp wear

Wear across all the lobes and rockers is a lubrication issue. "Back in the day" fuel dilution was a big issue. Carbs, mechanical injection and CIS systems can dump loads of fuel into the engine. This will dilute the engine oil over time. Infrequent oil changes and a rich running engine is a camshaft/rocker killer.

Since DME was introduced in the 80s there is less fuel dilution problems. The system is less vulnerable to being "tweaked" for massive rich running compared with earlier fuel systems.

If it were an oil quality problem you would most likely see wear on all the lobes on both the camshaft(s) and rockers.

To the OPs question. Yes that camshaft(s) needs replacement. Plan on a complete set of rocker arms too. Do not use your old rocker arms with a new camshaft unless you like the possibility of doing the job again in 10K miles.

[911pcars]

Not any oil with zinc and phosphorus. Can't add these elements to crap base oil stock.

[T77911S]

Originally Posted by safe

I'm pretty sure John W has more data points than this cam....

Pitted cams was never an issue before the zink and phosphorus content was lowered.
I've spoken to lots of old timers that has never heard of these problems back when these cars wasn't outdated.

I have to agree with DB.
you have ONE lobe that's trashed.
an oil quality problem will show on ALL lobes or rockers.

I go back to what I said.
chances are he had debris stuck in one of the spray bar holes.
I have had that happen twice to me.
once on my 930 when some of the coking broke free and plug the hole above #6 and trashed the lobe and rocker.
then on my 77s, saw a small piece of fuzz sticking out of one of the holes. did not totally block it like it did on the 77.

[john walker's workshop]

if a lobe is running dry, it will be dark and scored, not pitted, and the rocker will be badly worn as well.

[pmax]

Originally Posted by safe

I'm pretty sure John W has more data points than this cam....

Not questioning JW's vast experience, previous post was responding to Peter M's. However, reading between the lines into Mr Walker's post, one could conclude these other widely used oils such as the M1 15W50 are not recommended given Penngrade has about 1300-1500 ZDDP.

Pitted cams was never an issue before the zink and phosphorus content was lowered.
I've spoken to lots of old timers that has never heard of these problems back when these cars wasn't outdated.

Infrequent oil changes is a major factor IMO hence my query.

[pampadori]

So the pitting (or whatever you want to call it) location on the lobe is where it never contacts another piece of metal. Its not located on the lift portion, its on the closed valve location. Same as it was on mine. I think that is a clue as to what causes it. slippery zinc and phosphorous wouldn't really help unless they also have some sort of corrosion resistant quality. I don't think you would have any risk running the cams with this pitting since it is in that location and not where the rocker arm will actually contact it but sounds like most are recommending replacement.

[john walker's workshop]

It is on the tip of the lobe, not the back side.