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Subject: [none]
From: rchecca@domain.elided
Date: Thu, 19 Sep 96 09:33:53 EDT
>From: "RTALBOT" <rtalbot@domain.elided>
>Date: Wed, 18 Sep 96 14:49:57 est
>Subject: <E30><M3> Timing Chain life

>    All;

>    78k mi. on my '90. Just wondering what the concensus is on when the
>    timing chain need replacing. Is this a tough task ?

>    Thanks,

>    Bob T

Hi, Bob:

  I don't think there's any cast-in-concrete lifespan on timing chains.
People generally replace the chain, tensioners and all sprockets when
they build their 2.3's to 2.5's :^) My machine shop recommends
replacing everything all at once because the gears develop a wear
pattern and if you put a new chain on a worn gear, the resulting
contact area on the new chain is even less that it was on the old chain,
thereby putting the new chain under even more stress! The tensioners
which are made of a hard rubber get even harder over time due to heat
cycling. Eventually they get so hard that wear is accelerated. So,
it's recommended to replace them as well. The toughest part of this job
will be getting the sprocket off the crank. And equally hard will be
getting the harmonic balancer off the crank - the nut is torqued to
>300 ft lbs!


  Now back to your original question. Should you replace your chain
(and etc...) I'd say don't worry about it. 78K is not terribly high.
I've never heard of a single E30 M3 throwing a timing chain, and I've
seen some higher mileage cars used on the track (> 110k miles).


Of course, this is just my opinion. If you have lots of time this winter
to spend at this, (and about $500 for parts...) go for it!


Ron Checca
'90 M3 Street
'88 M3 Track
'88 M3 Stock (>For Sale<)
'87 325es Road