Bill Ball

Yes, I recall some fractures reported here and the results were disastrous. I do have the replacements and my intent was to do at least that. The low wear surprised me. I recall seeing 1/4th wear through at 200K miles. It maybe that the passenger (right) side is more worn. I appreciate you and Greg bringing that up.

Bill Ball

Oh, I do plan to clean the oil check valve and do its o-ring.

Dan87951

Bill does the car still feel relativity strong? Pretty cool to see one with so many miles. Hopefully you get another 100k out of her. Have you done any leak down or compression checks at this mileage? Just curious what the numbers would be on a high miler.

Lizard928

The first picture you show has a fair bit of lobe wear.

Rotate the cam so the lobe is all the way up or down and measure the base circle. Then rotate so the lobe is parallel to the lifter and measure again. Deduct your base circle size from the measurement with the lobe. This gives you max lift to compare against the factory document. I bet you'll be surprised by how much that lobe has actually worn.

I personally would be changing them/having them reground, but I'm **** when it come to them.

FredR

Just finished my evening cup of tea and whilst looking at the tea leaves in the bottom of the cup I could swear I saw what looked like a new set of high performance cams in Bill's near future!

Must say I also felt there was quite a bit of wear on those lobes but that could also be an optical illusion caused by flash or whatever. It would be interesting to know whether there is appreciable wear after 300k miles- cams last a long time but nothing moving like that lasts forever so presumably there is such thing as a reasonable life expectancy for these things whatever it may be.

Rgds

Fred

Imo000

You guys should see what really worn can lobes look like. Google TDI camshaft wear and you'll see what I man. My DD had a lobe worn to an almost perfect circle and the engine still ran fine. When the follower top wore through I noticed something was wrong. In my oppinion, Bill's camshaft are still perfect usable. There is too much scaremongering going on here. Great g's suggestion is good, leave them be and look at it again in a few years.

hacker-pschorr

Did you actually read the entire thread or just assume everyone is screaming they need to be replaced?

Go ahead and read all the posts again and point out who's trying to scare who here since I'm obviously missing something.

Mongo

Man... now I may have to go back in and replace them.

GregBBRD

You might be correct, there may be more wear on that right hand lobe than can be told from a picture, now that I look at it very closely.

Measuring is a good idea. Couldn't he jsut measure the entire height of the lobe from base circle to top of lobe with a pair of califpers and compare that with the other lobes to get a good idea of the amount worn off?

Lizard928

Not all base circles are exactly the same size. But yes comparing to other lobes is a wise idea.

With regards to Imre's comment, I've replaced those cams too. But once you see the lobe wearing off like you see on that one lobe. There is damage being done to the lifter under it, it is then only a matter of time until it's totally dead.
I've pulled cams out of a 270k mile engine with no lobe wear at all. I've also pulled cams out of a low mileage car that were toast. How and where it is driven, with the oil being used is the biggest determining factors in the life of a set of camshafts.

Lizard928

Once you start to see "smearing" on the lobes (shown in photos), that means that metal is being removed. As hard as the lifters are, they will wear through shortly there after. If it was just minor pitting, you MIGHT be able to continue using without any side effects. The smearing is another story.

If you measure the height of the lobe, and there is much material missing, consider having it reground or replaced. Inspect the lifters carefully, if there is any pitting, replace the lifter.

Imo000

How may reported cases of lifter top wearing through do we have for the 928? I can't remember a single one so even if there are some, the number must be extremely low.

Bill Ball

I'll do the measurements when I get back from helping George Suennen at an open road race in Nevada. If the lobes have lost lift, so be it, then I'll be up for replacing them. I've seen and measured worn cams before. These don't seem very worn. Also, as was asked, the motor still feels quite strong. I'm am not interested in high performance cams, at least at this point. I will most likely just get some fresher S4 cams and be happy.

Bill Ball

Colin:

I think what you see as smearing might be poor focus on the cam lobe as i was focusing on the rub blocks in that pic. And the possible difference between right and left lobes might be a light reflection artifact. Other than variations in pitting on the tips, the lobes did not look different to me. BUT i only looked at and photographed a couple of lobes that were in an exposed psition. I'll have another look at all the cam lobes and complete the measurements next Tuesday. And I will scrutinize the lifter tops. The car runs well without any lifter noise. Thanks for taking the time to review and comment.

Speedtoys

Bill: My old clean cams..are still yours man.