Push hard and live
Join Date: Apr 2007
Location: Carson City, NV
Im suffering a bit of bafflement. That's not unusual, but....
Are all of you guys sure about what you're saying?
All of the "vacuum advance" distributors I've known might better be described as "vacuum retard". They would get the maximum vacuum when the throttles were closed, causing the diz to retard from its static setting. This was to improve the idle performance, among other things.
As soon as the throttles opened, the vacuum would essentially vanish, and the advance mechanism would take over just like in other distributors.
This approach provides a wider range of spark timing, with a steep break in the curve at idle, specifically to improve drivability and a smooth idle.
In this system, the vacuum is generally taken just after the butterfly, as one wants max vacuum/max retard at idle. The vacuum port is close to the butterfly so the vacuum doesn't vanish all at once when the butterfly opens (Bernoulli). It works fine on a single barrel of a dual Weber system, if the Weber is equipped with the correctly placed port. Most are not. The DCOMs on my 102 have the single vac takeoff, but I don't use it.
I'm not familiar with dizzies that depend upon vacuum to manage all of the advance. In fact, since vacuum diminishes with increased throttle opening, the kind of diz you guys are describing would have to be set at max advance for static, requiring the "vac advance" pot to kick in pretty quick at the moment of start up.
I suggest further reading.
Carson City, NV
59 102 Touring (first Alfa $500 running)
65 Sprint GT (2nd Alfa, $500 daily driver)
102 Sprint (never did anything with it, but wish I had)
74 Berlina (first new car - now certainly rusted into oblivion)
61 Giulietta Spider G-Prod Race Car (where is it now?)
84 Spider Veloce (rarely drove it, so sold it)
86 Quadrifoglio (Dull car - no more 115s for me)
1971 Montreal "The Full Monty". Fair winds and following seas
59 102 Touring Roadster - restoration complete, enough Alfa for any rational man. Or irrational, for that matter
Two 1946 Stampe SV4C (c/n 294 "Rocinante" - wife's favorite airplane. RIP), and c/n 235 "La Bon Temps Femme" (gone to a new home, but never forgotten)
Zlin 50LA (+9 -6 gees, titanium spar, 1200 lbs, 260HP rumored to now be in Brazil)
1946 Luscombe 8A
Starduster Too (recently spotted at the Nevada City, CA airport - over 20 years and an entire continent separating it from our stewardship in Binghamton, NY)
1955 Cessna 170B (wife taught me to fly tailwheel in this)
64 Mooney M20E ("Rambo". My faithful steed for over 30 years) Nearly 50 years old, and just returned from a trip to Argentina in him
Newest in the fleet
1967 Piper Super Cub on Wipline amphibious floats (a true "all terrain vehicle")
2010 Triumph Thunderbird
You can snap roll an Alfa only one time...