Koenig928

Visual inspection reveled some interesting wear marks. These two photos show pitting marks on the tip of the lobes, but they are on the back side as the cam rotates. What would cause this?? Is it exessive moisture (the car could have sat not running for ??? before I got it..)? Or is it metal 'shavings' that wear normally and get dragged behind the lobe? These are the only places on the lobe that show this. There's no missing cam teeth or other chunks missing that I can see..

Anyone?

thanks.

Tony

Ive seen the little streaks, but not the ones you have circled.
Ive heard of pitting issues, i think it was on GT cams specifically?
I really wouldnt know what it look slike either.
Perhaps those that have seen or know better will chime in.

Are there corresponding marks on the lifters?

What cams are in there, do you know? Part number?

While your in there now put another seperator on the cam cover.

Lagavulin

As Tony stated, I have never seen S4 cams pit like that. On the other hand, I've seen both 85-86 and GT cams with those pits.

Get some part numbers off of those cams!

Koenig928

The cam number are here: [thread]https://rennlist.com/forums/showthread.php?t=206111[/thread] I started two posts on this...

If my Porsche Tech Spec booklet is correct, then the intake cam should be the Club Sport version. Perhaps same for the exhaust cam, but the last number is off (according to the booklet).

I've never seen this too. These marked areas look like they've been eaten into, I can run my dental pick over it - its a recessed area, so its not sticking up. Tried to insert a feeler guage underneath each cam lobe, but of course I couldn't get it in there.

As far as I can tell, there's no marks on the lifters. But there could be on the contact area - but I can't see 'em cause the cams covering it.

But its strange, these marks are only on the tip of the lobes, just past the max lift point (as it rotates), and NOT anywhere else on the lobe surface. The rest of the cam surfaces are all smooth with 'normal' looking wear.

Koenig928

try this one...

https://rennlist.com/forums/928-forum/206111-koenig-engine-cams-who-can-i-d-these.html

SharkSkin

Maybe that's not the stock grind.... they may have been built up and ground to a more agressive profile, not suitable for idling(like a lot of the more radical race profiles)

drnick

i had some pics posted of my GTS cams with very minor pitting at 36k km. cant find them at the mo cause ive been cleaning my desktop..

Vilhuer

Pitting in pictures look somewhat different than what is on my GTS cams for example. More 'normal' would have round craters and not chunks missing like in pics. Radius on cam surface sides looks normal though. This could mean they are stock and not regrind.

Few previous threads with pictures and explanation what causes pitting. Especially check Garth's pictures in Yahoo to see normal GTS cam wear pattern:
https://rennlist.com/forums/928-forum/169241-gts-camshaft-pitting-pic.html
https://rennlist.com/forums/928-forum/131765-s4-or-later-model-cam-pictures.html

Koenig928

Thanks Erkka, lots of good info there.

Did find the cam numbers, they are "Worldwide" cams on the early 32 valve engines.
https://rennlist.com/forums/showthread.php?t=206111

mark kibort

is this car an automatic?
sometimes lower ave rpms and thus lower oil flow can cause premature aging of the cam lobs.

Looks like these cams need to be replaced or at least watched.
mk

Koenig928

This car is a manual. Do you think cam wear varys between the two??

I'll definetly keep a close eye on the cam lobes.