[928uk] High Mileage Nervousness - Cam Chains

[marton hasenberg via 928uk]

I read a theory somewhere that the 4 pot motor cylinders are at a 
different angle than the 928 ones so the oiling pattern is different 
hence leading to this cam chain problem?
I believe the 4 pots were derived from the 8 and the design change 
required some compromises like, for example, the balance shaft.

Mit freundlichen Grüssen/ with best wishes

Marton Hasenberg
Rheinstrasse 2
8193 Eglisau
Switzerland

076 514 84 08
On 18/10/2015 00:59, Simon Crowe wrote:
> Hi Guys,
>
> The cam chains are an issue on the 944 S2 and 968, who's 4 cylinder 
> engines borrow the head and cam gear from the 928 32v V8's. No idea 
> why the four pots suffer this and the 928's generally do not. The 
> chains don't break but stretch, and then cause the cam shaft sprocket 
> to wear unevenly. Because the sprocket is part of the camshafts, the 
> final fix is to replace the two camshafts.
>
> Lots of advice on the net to routinely overhaul the tensioner pads on 
> these 4 pot engines, but I've not seen the same advice for the 928 on 
> a wholesale basis. Personally I've never replaced on either of my 
> cars. I like Rogers comment that suggest that the original chains are 
> better that replacements anyway.
>
> You will see that the uk sourced tensioner pads have 944 part numbers.
>
> On a tangent, I read somewhere that a guy in the US managed to install 
> the 968 Variocam system onto his 928 engine.
>
> Simon.
>
>
>
>
>
>
> On 17 Oct 2015, at 22:36, Paul via 928uk <928uk at lists.928.org.uk 
> <mailto:928uk at lists.928.org.uk>> wrote:
>
>> Nice one Marton
>>
>> Fortunately that only shows that I was aware of the issue some time 
>> ago, but didn't think my car would last so long that I'd have to be 
>> concerned about it...
>>
>> Paul
>>
>>
>> On 17 October 2015 at 22:32, marton hasenberg via 928uk 
>> <928uk at lists.928.org.uk <mailto:928uk at lists.928.org.uk>> wrote:
>>
>>     Hi Paul
>>
>>     Did a search and found this from 2009 - from someone named Paul -
>>     not sure it helps  :)
>>
>>     `
>>
>>     Oh dear God!
>>
>>     For what it's worth I use Penrite HPR15, and this is my reasoning:
>>     There was an informed debate on the Landshark list sometime last
>>     year about Oil. This basically seems to have concluded:
>>
>>       * Flat face hydraulic tappets (used in the 928 but not more
>>         modern cars) require levels of Zinc (ZDDP) that were present
>>         in oil until the mid 90s for protection
>>       * Modern Cats are poisoned by ZDDP, thus newer oils have lower
>>         ZDDP, older Cats such as those on the 928 are more robust
>>       * Newer oils also have generally lower viscosity to enable them
>>         to meet fuel efficiency requirements
>>       * 928 bearing failures are associated with low viscosity oils
>>         and hot environments
>>
>>     Following this I have decided to stop using generic 10W-40
>>     semi-synth, and switch to Penrite HPR15 (15W-60) which is approx
>>     £30 per 5ltrs.
>>     I hope others who were ignorant of the ZDDP issue will reseach
>>     this for themselves and reach their own conclusions.
>>     The chain sprockets on the cam shafts can lose teeth, this
>>     happens when the cam chains stretch. The standard advice is to
>>     replace cam chains if there has ever been piston valve contact,
>>     but I'm not sure whether there is a fixed replacement interval. I
>>     expect people tend to replace the chains when replacing the
>>     nylon tensioner pads.
>>     Paul
>>     87 S4 Manual
>>
>>
>>     Mit freundlichen Grüssen/ with best wishes
>>
>>     Marton Hasenberg
>>
>>
>>
>>
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>>
>>
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