Camshaft Wear...Opinions Please!

[willg54]

Cam cover has come off tonight and on close inspection there seems to be some pitting on the exhaust cam lobes and on a couple of followers.

Can you give me your opinion on this..should i swap? My intuition says change. if its already started to wear, they're only going to get worse.

If i do change, whats the best route? standard, 7a or RS2? Inlet looks fine by the way...so im guessing 7a exhaust.

[Error404]

hmm, not seen pitting on an I5 cam before. It usually happens a bit further up the lobe when I've seen it - the pits eventually form craters in the surface.
RS2 exhaust cam seems to be the one to go for if you can find one

[driftin jo]

They are fine, no wear to speak of at all , the little holes you see are not wear, they are inclusions from when the cam was cast , believe it or not cams with these inclusions in pass final inspection if they are less than a certain size. They do not cause accelerated wear characteristics if below a given size and location. They are generally only allowed if they are in a low load area ,base circle or ramp on part of the cam . If the cam had an inclusion after grinding that was on the top half of the lobe (lift area) the cam would have been scrapped.

[willg54]

It did cross my mind if they were from manufacture as they aren't near the peak lift where you'd expect them to be.

if you look on the first pic, you can just see the pitting in the follower...any thoughts on that?

I've been developing cams for my final year project at uni, ill have to post up some of the work ive done. All the analysis of force, velocities, accel etc and found about 10-12% torque for our engine!

[driftin jo]

It did cross my mind if they were from manufacture as they aren't near the peak lift where you'd expect them to be.

if you look on the first pic, you can just see the pitting in the follower...any thoughts on that?

I've been developing cams for my final year project at uni, ill have to post up some of the work ive done. All the analysis of force, velocities, accel etc and found about 10-12% torque for our engine!

They will probably be OK but it is hard to tell from the pic, I must admit I would be more concerned by the followers in this case .
There was a time when the likes of AUDI ,VW , BMW etc would bin any part cast with an inclusion in of any size. Somewhere along the line quality was compromised, if only a little in this case, most likely by accountants, rather than engineers, in name of making more money.

[Error404]

I always though that these kind of imperfections lead to more serious spalling or is this a bit of a myth Jo?

[s2driveruk]

really interesting thread, feel i am learning something already on a sat morning

[willg54]

i've just got the feeling this is going to get expensive

I didnt want to do anything engine wise for 12months so my budget can get it back on the road...but atleast i can possibly start doing it all sooner 450bhp here i come

[willg54]

I've spoken to Will at VRS and can get sorted with 7A cams and a set of tappets at a very good price.

i think that conversation is going to cost me alot....im tempted to open the whole engine up, new rods, bearings, arp studs.....

[Error404]

Thats a £2k can of worms right there mate

[driftin jo]

I always though that these kind of imperfections lead to more serious spalling or is this a bit of a myth Jo?

I have seen cams with inclusions in like Willg54's pics in thread before and checked them 50k miles later and there was no change / wear to the cams at all, this would be the thinking of allowing the cams to be put in the engine in the first place, however this does not mean that there were not larger inclusions just say 5 thou below the finish grind that simply fell out after a few thousand miles to reveal a large crater that would definitely cause excessive wear , a possible scenario in the case of your pic. This could a course happen if there had been no viable inclusions at all when the cam was installed . The pic you posted is the worst I have seen as out of all the Audi's I have had (some very neglected prior to my ownership, no oil change etc) I have never seen any wear to worry about gegenerally.illg54's cams in my opinion will be fine for another 100k at least , but each to there own, they are not perfect , but as I say they were like this from new.

[Error404]

[willg54]

bit more investigation this morning and some clearer pics











I think driftin_jo is right and that these were probably defects from manufacture and not a direct result of wear. A defect under the surface such as an air bubble would eventually surface itself but in doing this it has worn past the hardened surface finish. They may last another 50-100K but i think for peace of mind, i'm going to swap the exhaust cam for a 7A cam.

Inlet cam side looks perfect, not a mark on anything, including the followers.

I'll be putting this back together with new tappets and a 7a exhaust cam

as for the rest of the engine...im going to hold myself back for 12months when im employed...not a student!