Non-rod Knock Fixed: Timing chain tension adjustment

[Scott Fisher <sfisher71@domain.elided>]

I just did perhaps the easiest maintenance task I've
ever performed on an Alfa: adjusted the timing chain
tensioner on a 2L.

Since the, er, rod knock, er, discussion of the last
few weeks, it's come to my attention that the Spider
had a rhythmic tapping rattle, right about 2500 RPM. 
Most Alfas I've driven/ridden in seem to have it to
some degree or another -- but since acquiring the
Berlina, it's become apparent to me that the Spider
was a LOT noisier than the Berlina at that precise
RPM.

So I looked up the procedure for adjusting the timing
chain.  It is SO EASY, with really only one tip of
note.

The timing chain tension on 2L engines is on the front
of the cylinder head, directly below the intake
camshaft.  On my car, it was a 14mm bolt just below
the large Allen-head plug.

1.  Start the car and let it warm up fully -- that
seems to be important (see below).

2.  With the car idling at normal speed (~800-1000
RPM), loosen the adjustment bolt.  (How loose?  I
rotated it probably haf to three-fourths of a turn, so
that it took no real effort to turn the wrench.)

3.  Let the car run for one minute.  Do NOT (according
to the book) let the RPMs go up during this time.

4.  Tighten the adjustment bolt.

Warmup (this is the "below"): I tried this the first
time while the car idled but was still warming up,
then went for a short jaunt around the neighborhood. 
There was still the 2500-rpm hollow clatter sound.  So
I let the car fully warm up, drove back to my
driveway, and repeated the procedure, then repeated
the test drive.  MUCH better.  There's still a barely
noticeable vibration right at that speed, but the
volume has been reduced by about three-fourths.  

I already had the 14mm wrench, so this job was
essentially free except for the small amount of fuel
used to start, warm up, and road test the car.  Apart
from the time spent warming up and road-testing, the
actual procedure takes about 90 seconds: 15 seconds to
loosen the bolt, 60 seconds to wait for it to adjust,
and 15 seconds to tighten it.  

If you haven't done this in a while and you notice a
little clatter (sounds sort of like valve-train rattle
in a pushrod car) at 2500 RPM, it's something to try. 
The owner's manual for the 1974 model year recommends
adjusting the timing chain tension every 6000 miles,
in which case I'm quite a bit overdue.  

Oh -- since somebody mentioned it recently, I also
checked, and there's no rattling from my 0170 cap. 
Nice and tight, just like it should be. :-)

--Scott Fisher
  Tualatin, Oregon
.
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