Lizard928

I had a fellow bring in his 1991 928S4 in to do a simple valve cover swap.
Replace the leaking seals, and swap them with freshly coated covers.

However once the covers were removed it became sad.
Almost every single lobe had damage.
Pictures of the carnage are attached.

We decided to install a new set of stage II camshafts into the car along with valve springs.

However does anyone have any idea as to what might have caused this?
Danny thinks thin oil with too little ZDDP. It was clear that someone had recently been in there and all the bolts were LOOSE. Along with the water bridge bolts. But the cheesehead ones were all tight with no sign of disturbance really.

blown 87

Those are done, for sure.

I had a guy come into the shop today with a S4, or says he owns a S4, I have never seen it and he wanted to argue with me that 15-40 was to thick of a oil for the car, he TOLD me I was wrong for using 20W50.
I see cams and lifters in his future, maybe even a engine.

Lizard928

Also I checked the stamping they are 271/2/3/4 00 So 88 and newer S4 cams.

ROG100

Thin Oil but also low ZZDP will do that. Zinc is what is important to our engines and I am no longer confident Mobil One has what it takes. That is the reason I use Royal Purple 20W 50 plenty of ZZDP.

928er

low zddp as mentioned but another thought is that maybe at some point the cams were replaced and the lifters were not? just a thought.... I also saw a 928 for sale as a parts car where the cam covers were off the engine, and it was parked outside.... if someone just slapped some cam covers on it and then fired it up with all the grit that was there it woudn't take long to do that kind of damage. has there been any discussion of pulling the heads and looking at the valve guides?

toofast928

20 years of "dry starts" will do this also.

GregBBRD

Also, '91s have the oil cooler under the radiator.

Great idea for the Autobaun.

Really bad idea for traffic.

Not uncommon to see oil temperatures over 280 degrees on hot days in traffic.

Combine that with thin oil, low on ZDDP, and you've got mega camshaft wear.

I've also seen a fair amount of oil thermostats that have failed on these engines.

I personally think that they get too hot and fail....

BTW....I've not seen any this bad.

Speedtoys

WB Greg!

dcrasta

Nice Pics. Those lobes look terrible. Mixed parts (old and new) and contaminated oil could contribute. Do you have any idea how well that car was maintained?

danglerb

My guess is with oil film failed since the damage seems right at the point of max pressure and not so much anyplace else. I wonder what else might be lurking?

Strosek Ultra

About low ZDDP.

http://www.ttalk.info/Zddp.htm

jpitman2

One thing about this ZDDP being needed in older flat tappet engines has me puzzled. Many modern engines are running direct cam-on-bucket flat top lifters - why do these NOT seem to need high ZDDP oils? I cant see a difference in the cam/lifter interaction or loads. My Suby DOHC has plain buckets (NOT hydraulic), and it can use a variety of ordinary modern oils apparently - I have seen the dealers use LL01 Softec (now BMW badged), and a couple of Castrol grades...has used none in 55k mi, and no tappet noises.
Whats so different here?
jp 83 Euro S AT 54k

RKD in OKC

Have 3 friends that had cam shaft failure on their cars in the last two years. All different makes. Have never heard of cam failures on cars BEFORE EPA took the zinc out of oil.

blown 87

I always put a can of BG MOA into every European car that gets a oil change here.
Sure can not hurt.

z driver 88t

Looks like at least until very recently the Zinc in Mobil 1 was still good, at least on the VOAs for the SM 15W-50 stuff many of us are using. Seems to be a little concern over the recent switch from SM to SN. I could only find one VOA on the new SN version of M1 15W-50.

http://www.bobistheoilguy.com/forums...64#Post2365764