Camshaft pitting!

Solo2driver · Aug 13, 2005

I was checking the oil today after a long and hot PCA (Porsche Club) autocross in San Diego in my '82 924 Turbo (2.0L CIS)....won GP Class, BTW

Noticed that directly under the oil filler cap is the lobe for #1 cylinder, and usually the lobe is actuating the valve so I can't see its lumpy side. Today it was up, and there are distinct wear marks and small pits near the apex of the lobe. There are no rockers and the valves are directly below the cam lobes. Engine has 60K miles on it, sparkly clean inside and out, no leaks, no consumption, no abnormal valvetrain noise.

Running Royal Purple 15w-40 for about 2500 miles, time to drain and get UOA? What should I run in the mean time? Doug says M1 T&S 5w-40, but I'm thinking that the 40-wt may not be cutting it. I don't want to over-thicken the turbo feeds, as running a "heavier" 50-wt has *traditionally* spelled the end for these finicky oil-cooled KKK Audi turbos.

I have all weights M1/EP, RP/Racing RP, RedLine, and Motul at immediate disposal to me...what to do?

-JamesW

Vspec · Aug 13, 2005

Redline, I love there oil. Excellent ****, Royal Purple does nothing for me.

Doug Hillary · Aug 13, 2005

Hi,
James - cam pitting is not "normal" but is quite common in low use engines. It is caused by corrosion and metal fatigue and occurs "regardless" of the oil used

Pitting is considered to be "damage" but minor pitting without excessive wear across the lobe is "acceptable" but should be monitored

It is lessoned in most cases by using HDEOs of a suitable viscosity. This is why I always advise using HDEOs in low use engines and have done for decades

None of the oils you mention will be better than another - it is significantly "use" related but a modern HDEO will moderate it!

UOAs will NOT "show" a pitting trace!

Regards

Doug

jorton · Aug 13, 2005

1 quart Mobil 1 10w-30 mixed with Mobil Delvac 1300 15w-40.

radiometer · Aug 13, 2005

Doug,
I really appreciate your information on cam pitting on low use engines. One of my cars isn't getting a lot of use now. I'm going to make sure I drive it at least several times a week now. Do you believe that is sufficient to protect against cam lobe pitting?

I'd like a comment on your idea of a low use engine.

Your comment on the DHEO for such is well taken note of also. Thanks.

oiler · Aug 13, 2005

What is a HDEOs oil? I have a new Toyota truck that I really don't drive but once every week or normally once every two weeks. I use a different vehicle for commuting.... This post just got me thinking. I have been useing Havoline 5-30w dino. Oiler.

TooSlick · Aug 13, 2005

Pitting, (a form of stress corrosion) is caused by selective removal of the "crystal lattice" on a loaded surface. The microstructure of the material is such that there are regions that are more susceptable to this type of wear.

I'd try a formulation that does NOT use Moly in this case. Either Delvac 1 or the Amsoil 5w-40 would do well here, I believe....

Tooslick

moribundman · Aug 13, 2005

quote:

UOAs will NOT "show" a pitting trace!

Are the "chunks" that come out too big to show up in a UOA?

unDummy · Aug 13, 2005

What to do?

Replace the cam and related parts....
Inspect the entire oiling system and improve it if possible(more PSI, more GPM, more cooling).

Solo2driver · Aug 13, 2005

Thanks for the responses, I think I am going to drain the RP 15w-40 and try M1 T&S for the next drain...it has been my plan all along to test different oils at my disposal to find the right one for this car...my old Merkur had an odd taste in Motul synth-blend 10w-40 which seemed to work well. This is the first oil that I have used in this Porsche, so on to the next one! RedLine is a little pricey, as is the RP Racing oil, but I plan on testing those as well.

This car is daily driven, but saw intermittant use before I had owned it. I will keep an eye on it. If all else fails, I may replace the cam when I do the timing belt and gear (they're cheap from Performance Products in CA) and get a better baseline in the future. I'll get pics if I can, but the pitting sure is small (I've just never experienced it before!)

-JW

AndyH · Aug 14, 2005

quote:

Originally posted by oiler:
What is a HDEOs oil?

HDEO = Heavy Duty Engine Oil

A couple of examples would be Mobil's Delvac 1 & Chevron's Delo 400.

bruce381 · Aug 14, 2005

Originally posted by Kestas:
[QB] It could just be from corrosion, but if the engine uses roller followers, your cam could be experiencing what is called "Hertzian stresses" which results in a unique phenomenon called "microstructure decomposition". I've documented dozens of such cases in bearings. In layman's terms, the repeated cyclic stresses on the surface alters the material microstructure making it more prone to subsurface cracking and spalling.

I think this is the answer along with wear particles causeing whats called "3 body abrasion"
this abrasion and fatique stress caused by elastic deformation on the cam lobe will cause micro cracks which will open to micro pits then the wear debris which may show on a UOA or a ferrograph "microscopic picture" of the oil will show the "chunks". This will cause the scuffing wear that runs in the direction of rotation. The best answer is to change oil often to remove debris in the system then get a better filter both air and oil also a higher vis oil will help go 1 grade higher.
bruce

LarryL · Aug 14, 2005

Have you tried a dose of LC? Sounds like corrosion not wear.

JohnnyG · Aug 14, 2005

quote:

Thanks for the responses, I think I am going to drain the RP 15w-40 and try M1 T&S for the next drain...it has been my plan all along to test different oils at my disposal to find the right one for this car...my old Merkur had an odd taste in Motul synth-blend 10w-40 which seemed to work well. This is the first oil that I have used in this Porsche, so on to the next one! RedLine is a little pricey, as is the RP Racing oil, but I plan on testing those as well.

Finally! Another Merkur owner! Where is the "old Merkur" now? I'd sure like to find another one. I really miss my '86.

Doug Hillary · Aug 14, 2005

Hi,

Kestas - James' car does not have roller actuators and some older low use Porsche engines do suffer cam pitting. Many engines have then covered hundreds of thousands of kms after this is noticed and in a different use cycle without further deterioration

Bruce - we are not talking about wear here - we are talking about "pitting". If excessive wear is associated with the pitting your comments are most valid IMHO

Typically, Porsche engines are low use in the hands of the first owner. This low use initially causes the cam pitting which is very common in the Porsche family of earlier coolant cooled engines. I have no evidence of a cam failure in such engines

Most Porsche engines do not have an excessive cam wear problem - such cam wear is virtually non existant

Moribundman - sorry, no "big chunks" with corrosion pitting referred to in here. However, at an advanced stage it would be wise to cut open the oil filter at each OC and check for related debris

It is important that a Porsche Approved & Listed oil is used in all Porsche engines. At the very least use a synthetic A3/B3 oil of the correct viscosity - at the most a synthetic HDEO 5w-40 lubricant is ideal

krholm - in Porsche circles "low use" may be only 2-3k per annum and this is quite common. Generally a lot depends on the engine's metallurgy of course but IMHO unless an engine is used weekly (taken up to operating temperature for around 30minutes) then the low use definition may apply

Castrol make special Vapour Phase Inhibitor lubricants (HDEOs) that are ideal in such cases
The vapour covers the areas above the oil line

Regards
Doug

427Z06 · Aug 14, 2005

Imagine that, a synthetic HDEO 15w40 didn't prevent corrosion pitting in a low use vehicle.

Otherwise, Doug is right on the money. Here's some related info:

http://www.sacskyranch.com/camshaft.htm

http://www.sacskyranch.com/corrosion.htm

Doug Hillary · Aug 14, 2005

Hi,
427Z06 - you said;
"Imagine that, a synthetic HDEO 15w40 didn't prevent corrosion pitting in a low use vehicle."

As you know the problem with James' car commenced years ago. The first time the engine ever saw an HDEO was probably 2005 - just before they changed the description DHD1 or whatever and just before Ted realised that A3/B3 was not a bra size!

Has Texas become more Democratic?

Regards

Doug

Big O Dave · Aug 14, 2005

quote:

Originally posted by Doug Hillary:
As you know the problem with James' car commenced years ago. The first time the engine ever saw an HDEO was probably 2005

I'm nowhere near as smart as you guys, but this is what I was thinking, too.

Solo2driver · Aug 14, 2005

Oooh, banter over my engine. I feel important.

Bought a jug of M1 EP 15w-50 and a MANN filter today. It is so hot around here that I am still a little worried about running a XW-40, gas prices be ****ed at $3.03/gal for premium (and yet VP Motorsport 109 is still $5/gal!).

Yes, this was the first time that I know of the car has seen a HDEO, but appeared to be well-maintained but sadly not driven enough.

"The Old Merkur" was my hugely-beloved 1987 Merkur XR4Ti that had been fully restored and in perfect working order. I was spending about $750/month in fuel just COMMUTING to work a year ago and couldn't handle it....no place for storage, and then a mysterious fuel pump failure and heavy transmission whine (T9 takes just 08.qts gearbox oil!!) was the nail in the coffin. I regret selling the car, and will always be looking for another clean one to restore. Too many are beat and rusted out.

Ah, German turbo cars of the 80's.....

-JamesW

bruce381 · Aug 14, 2005

Originally posted by Doug Hillary:
[QB] Hi,

Kestas - James' car does not have roller actuators and some older low use Porsche engines do suffer cam pitting. Many engines have then covered hundreds of thousands of kms after this is noticed and in a different use cycle without further deterioration

IMHO Doug do not insult my intelligence or my expertise I've been doing this for 32 years.

"Bruce - we are not talking about wear here - we are talking about "pitting". If excessive wear is associated with the pitting your comments are most valid IMHO"

Sorry Doug but pitting other than from corrosion is due to a wear issue. Formed as I said from hard wear particles being pounded into the cam or lifer lobe that causes micro cracks that causes micro pits that causes pits that caused spalling.

This has been studied and pitting is one of the reconized wear classes.

bruce

Camshaft pitting!

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