Does anybody have a list of advance curves for Marelli distributors, IE: S155AX, LX, S135, S178 etc.
Sounds like you may have too much total advance if your optimal low speed advance results in too much high speed advance. That is the issue I had so I needed to keep the centrifugal advance mechanism from moving too far.my car (128 coupe 1300) had the OEM S135 fitted, i swapped it with a marelli SE100CX (breakerless), and it works really better (i guess the old dizzy was very tired tough)..now i'm in the process of making some test with the static advance\vacuum..generally i found that more advance= better low rpm oomph, but engine stall\become rough around 4000-5000; less advance=nice fast revving build up (wow: feels like a japan 4 cylinder bike!), but lazy before 4000..would be nice to get both worlds.. but looks like is not so easy
Yes, I was using a timing light with an advance knob on the back. The Ducelier distributor has a lot of centrifugal advance to compensate for the vacuum retard. I created an advance stop by using a heavy spring filled with JB Weld that creates a rigid link. The outer hook on the spring is connected to a post. You can bend the post to control how much advance you can get. Seems to work OK...another problem: the vacuum..in my dizzy it produce a max advance of 12° (max manifold vacuum should be at idling\throttle closed with the car running?) but i know that the old ducellier (points) had a retarding vacuum..maebe that's why when you disconnected the vacuum it resulted in too much centrifugal advance?