Re: Exhaust stuff

[erict@cta.com (Eric Thorstenson)]

Scott said:
----
>   I also took the chance to examine the head. The rearmost bearing on the
>camshaft was very grooved. All others were fine. What would be a good course
>of
>action to take on this and should I lap the valves or replace the stem seals
>while I have it out? Keep in mind that I don't have a ton of money to spend
>right now, but I plan a complete rebuild of the engine in 6-12 months. By
the
>way the car has 150,000 miles. Thanks in advance for any suggestions.

Common problem of an overtight cam belt, puts strain on the water pump
bearing, and pulls on the cam gear (not a good thing, btw).......  do the
head while you are there. your valve guides will be going soon anyhow.....
----

Scott - I haven't been into nearly as many Audi engines as
you have, so I can't argue the BTDT factor, but I'm not sure
the math bears you out on this one.

If we assume a (pretty high) value of 200 lbf for the force
applied to the cam by the belt, even doubling that value is
going to translate into only an additional 25 lbf or so at 
the rear journal. Hard to picture that causing scoring.
Even at the front journal, where doubling the belt tension
would add approximately 225 lbf, that's still small compared
to the nominal load capacity of journals this size (ballpark
2000 lbf).

Any thoughts? Real-world Audi peculiarities I'm not aware
of??? I'm particularly interested in this because my 5kS
also appears to have some slight scoring at the rear
journal, which I can't quite explain...

Eric T.     '86 5kS
erict@ra.cta.com

(BTW - if anyone has their Bentley handy and wants to
look up belt tension and bearing dimensions, we can improve
the accuracy of these numbers.)