re: Distributor - kaput or OK?

[Scott Fisher <sfisher71@domain.elided>]

--- John Dohrmann <jdohrmann@domain.elided> wrote:
> I'd suggest replacing the distributor if there is
> any side-ways play at the
> rotor, based on my own experience in my 1986 spider.

John's advice seems good.  I recently replaced the
distributor in my '74 Spider and found some very
useful information at the AROO Web site when it came
time to put the new one in:

http://www.alfaclub.org/techstff/tuneign.htm

There are some illustrations there that may or may not
apply to the distributor/engine in your car -- for
example, there's a drawing of a Marelli distributor
with dual points, indicating one for advance, one for
retard.  I don't know what years came with that
distributor, but neither the old Marelli nor the new,
er, less old Bosch that I put in its place had such a
setup.  Likewise, the timing marks on the pulley
apparently vary from market to market as well as year
to year (see Figs. 4.4 - 4.6).

Useful diagnostic tip, while we're talking about
distributors: if your car starts fine and runs well to
the redline but has a stumble or hesitation at ~3500
RPM, check your distributor advance mechanism.  I
don't know whether the one I took out of my Spider was
original, but the pivots on the advance weights had
worn to the point where advance was very sloppy,
causing rough running at 3500 RPM.  Soldiering through
that level caused things to smooth out again, which
was my clue that the advance was to blame -- the
reasoning being that when there was no advance or full
advance, the settings were correct, but when there was
partial advance, the slop in the mechanisms caused
timing to jump around.  

How to check the mechanism: pull the cap and turn the
rotor lightly by hand.  There should be even, moderate
resistance when you try to turn the rotor (up to the
limit of the advance mechanism, at least, at which
point it should feel immobile -- I would think it
would be very difficult to turn an engine over by
twisting the distributor rotor with your thumb and
forefinger...).  If the rotor feels sloppy, loose or
even rattles slightly, it's probably time for a
rebuild or replacement.

Local (Portland) Alfa mechanic Nasko told me that it's
been a long time since he's seen advance rebuild kits
for the Marelli distributors, so he set me up with a
good used Bosch with new electricals, which I
eventually bolted into the car and oriented correctly
(#1 is in a different place on Bosch and Marelli
distributors...)  

As a final tip, the nifty T-handled distributor wrench
comes in handly for this job, but if you can't acquire
one in the time allotted, a 10mm crows-foot attachment
on a 24" ratchet extension would do the trick.  As my
wife is fond of saying, it isn't a proper sports car
unless it requires special tools...

--Scott Fisher
  Tualatin, Oregon
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