Vacuum advance module for Marelli

[wetminkey]

It has come to my (and a few other's) attention that the vacuum advance modules for Marelli distributors are adjustable. They come with an 'undetermined' amount of advance adjusted in.
They can be installed as is, but 'we' (geospider) have come up with a theory for a more proper adjustment on installation (since the distributor must be pulled to make any changes):
The diaphragm actuating rod should be adjusted to a length so that the mounting screw holes line up and it does not change the position of the ignition advance plate ball when snapped onto it. That way vacuum advance will begin at zero.
The full development of this thread (with answers from AutoRicambi) can be found under the 'MSD 6A Ignition Control' post in this section. Check that for a lot of great ignition recommendations,...of all types.
I hope this helps some folks!
Todd.

[toyfiats]

This was covered years ago on mirafiori.com by Dave Voss. I've kept a snipit of the thread ever since for reference.

Re: How to set shaft length when replacing vac advance
From: Dave Voss (Napa Valley, CA)
Email: d.v.voss@gmail.com
Date: Tue Oct 30 12:00 PDT 2012
Hi John, the plastic end on the vacuum advance shaft spins along the threads
to set the 'reach' that it has for attachment to the ball connection on the
bottom of the pickup plate inside the distributor. Proper length adjustment
is when the tip of the plastic end (as attached to the ball connector) is
close to (but not touching) the end of the channel in the distributor body.
This ensures that the full length of that channel is available for the ball
connector to move without bottoming, which would prevent full vacuum advance.

[geospider]

Well covered Todd. that is exactly how I adjusted it and seems to make sense.
If anyone is replacing because of a failed diaphragm, but otherwise had been working (who knows how long it wasn't), adjust the length to match what you took out. Then check that the dizzy base stays at "zero" when attaching/setting the screws. Actually pretty easy to do.

I like that these types of posts come back around. It can be hard to find the old stuff. I looked.
Also, kinda fun for us newbies to to add to the knowledge/experience on this site.

Thank you as well toyfiats
Geo

[wetminkey]

I'm just STOKED that I was able to help, and to provide a searchable thread on this subject!
I absolutely hate the idea of anyone else having to "re-invent the wheel"! We've got computers, forums, and search available to us now, we should take advantage of it all!
Being retired, I'm going to do my best to add to this site whenever possible, and with lots of pictures.
I know most vehicle systems, including carburetors, and have restored a number of vehicles, so I hope to provide as much of that information as I can to the members here. I've already been able to permanently add information to Mirafiori, with the help of members of this forum!
Happy Motoring!
Todd Compton.

[Frog2Spider]

More on this issue ...
I found that the rod on the new vacuum pot would only allow the rod to move about 3/16 of a inch, while the advance plate in the distributor had a total movement of approximately 1/2”.
I adjusted the plastic connector on the vacuum shaft so that the plate would be pulled to the ‘full advance’ position, which of course does not allow the plate to move all the way back to its ’relaxed’ or what would appear to be the ‘0’ advance position.
The travel distance of the rod is less than what it would need, to obtain full travel of the plate, from ‘0’ advance to full advance. But, wow, what a performance difference now that I’m getting the full advance!

Dave.

[dinghyguy]

did you reset the timing as well? presumably at the new not quite 0 position?

cheers
dinghyguy

[wetminkey]

But don't get too 'HIGH' on over-advance,...you've only 'cheated' the distributor out of it's total, and reduced your mpg in the meantime,...
Your engine will run too cold.
Set that vac advance to zero travel at rest as described,...you will like the result!
Todd.