EMan 928

Here are some pics of my GTS cams. Do they look normal? Are they supposed to have the gray wear lines?

PHIL928

I believe that is normal. Infact I believe those are in very good condition, no pitting at all.

Mario928

..

Charley B

Hi Eric

I sure hope Phil is seeing it correctly. Maybe someone like Greg Brown will weigh in with an opinion.

I forget which hole had a lower compression reading, but I'm curious what you found with the valves and rings on that cylinder.

I had a sinking feeling when I saw your question, but I'm keeping my fingers crossed for an awesome outcome.

Best of luck,
charley

Lizard928

Looks like pretty standard wear.

FBIII

Isn't the grey the original finish and the shiny area where the wear is? On the first picture of the lower cam, is there some minor pitting on the lobe just to the right of the chain?

docmirror

Cyl 7 intake furthest from cam chain sprocket looks like it has pitting on the nose. Hard to see for sure, but the left side of the nose appears to be pitted. Normal, and may not be an issue.

Jim M.

That looks like normal wear to me and less pitting then on my GTS cams when I installed the GT cams.

UpFixenDerPorsche

I'll be more than happy to be shot down in flames (had lots of practice, but I don't think anything there looks healthy: the lobes, base circle, bearing.

There's wear where there shouldn't be (base circle) and uneven wear where it should be (lobes and cam bearing). Pitting on the point of the far right lobe in 2nd pic.

Looks like there has been momentary oil film failure leading to fine scuffing.

Any oil pressure problems? Oil got lots of ZDDP?

Maybe it's just the way the light is in the pic.


Cheers

.

UpFixenDerPorsche

Scroll down to the last topic: Update 2008.

http://www.aa1car.com/library/camshafts.htm





.

Lizard928

Upon further inspection (on phone earlier) there is some wear to the cam lobes which should be removed.

Bill Ball

Interesting. I was going to say these looked pretty bad to me, but I've only seen a handful of used cams in my life and none with this rough of a finish whether new or used.

EMan 928

Thanks Charley. Greg did say he thought this looked like the normal coating that came on the cams.

It was a good thing we took the heads off. You wouldn't believe what the carbon buildup was on top of the pistons and around the valves. No amount of BG treatment/Techron/Seafoam was going to remove the carbon buildup that was there. Also, the head shop said I had 10 bent valves (minimal but none the less bent). Plus, the inside of the intake was coated with an abrasive oily mixture ( I will post pics later). This car was ingesting a lot of oil. I can't wait to see what it will run like once the carbon is removed and Greg's crankcase vent system is installed (along with Greg's header/exhaust setup)

928mac

Here is what mine looked like and on the very tip there is some pitting


But I used some 400 grit scotch brite pads like these
http://www.3m.com/product/informatio...-Hand-Pad.html

and this is how it turned out.





So that said I dont think your cams are that bad but it is also hard to tell in a picture.
Also as you can see, most of the embedded material in the cans will polish off.

My 2 cents

.

GregBBRD

Eric sent these pictures to my private email and I responded to his questions there.

Here's what I basically told him.

This is totally normal....they all look this way, unless you completely remove the protective/break-in coating, like Brad did.

The cam maker, for Porsche, put some sort of coating on the cams, originally, to help with break-in. In the areas where the cam contacts the lifters with high force, the coating wears off. In lower load areas....on the "ramps" and base circle areas...the coating stays for very long periods of time.

There's not enough pictures of the tops of the lobes, for me to draw any conclusions about wear.

Some notes about the "pitting" that is very common on 928 cam lobes:

I've yet to see a camshaft that was worn beyond use on a 928 engine....I've never even seen a single "flat lobe", on a 928 cam. I've seen some pretty "nasty" pits and I've swaped out cams that had severe pits....but nothing beyond this. I've seen dozens of flat lobes on welded 911 cams and "hot rod" American V-8 engines. The 924 engines "chewed" up cams at a very high rate....destroying both the lifters and the cams. I've seen a few flat lobes on stock 911 cams.

Solid lifter cams are harder on the lobes than hydraulic lifter cams. On a solid lifter cam, the "clearance" between the lobe and the lifter can decrease....which doesn't allow enough oil to get between the lobe and the lifter. Hydraulic cams maintain the clearance between the cam lobe and the lifter.....allowing oil to get between the two....reducing wear.

In summary, I've Never seen a flat lobe on a 928 cam. If you've got small "pits" forget them. I use an oil with 1200 ppms of Zinc and Phosphorus (minimum) to protect the cams.....until this is completely proven to be untrue.....or the oil companies come up with an alternative additive.