Re: Non-rod Knock Fixed: DANGER WARNING Timing chain tension adjustment

[Bernie & Diana Bennett <bennetts@domain.elided>]

Lucky Scott:

Others BEWARE! You may not be as lucky as Scott. He followed the procedure
in the owners manual to adjust the tension. Many others have used the same
technique and damaged $$$ their valves. A safer Recommended method by many
is to do the tensioning with the engine off. No accidental slip on
loosening the bolt and no accidental surging of the engine speed. I repeat
others have damaged $$$ their valves when adjusting wilst the engine was
running/idling.

Best Wishes,
Bernie Bennett

Scott Fisher wrote:

> 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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