I have been having trouble posting to the IML lately after resubscribing
and changing to digest mode. I wanted to share these comments I sent to
Geoff in case it might help someone else.
Geoff;
Have you had your existing distributor apart enough to see the
mechanical spring loaded advance cams? If not, remove the points and
the points' mounting plate and check the movement of the spring loaded
cams. The cams should move easily by finger pressure and quickly return
to their resting position. The pivot points of the cams are lubricated
and it is possible that the lubricant has dried out. This can happen on
both conventional older design distributors and the newer electronic
distributors. It shows up as knock or ping under acceleration. Check to
be sure the vacuum advance and vacuum lines have no vacuum leaks I had
a '73 model with electronic ignition which would act that way. I
eventually discovered the problem with the cams when I started to
replace the pick-up reluctor mechanism and star wheel on the distributor
shaft. Before replacing the parts I decided to clean and re-lubricate
the cams and it corrected the ping/knock problem. I went ahead and
changed the reluctor element and the star wheel on the distributor shaft
anyway since I already had the parts on hand.
The car I mentioned above had the exact symptoms you described - pinging
under moderate acceleration. If you really got on it, the pinging would
go away. It pinged just when you did not want to put your foot into it,
just normal driving. It is a subtle condition and difficult to analyze
except by just removing that upper plate and trying moving the
counterweights/cams to see if they move freely and quickly, not slowly
(caused by dried out or gummy lubricant). I hope this helps.
Joe
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