Are VW backwards ??. . . So are VW distributors Backwards ?
VW's aren't backwards, all other makes are! :lol: There are lots of different distributors for air-cooled VWs but the most common are the 009 (double-o-nine) and SVDA (Single Vacuum, Dual Advance).
The 009 is a purely mechanically (centrifical) advanced distributor. The faster the engine turns, the more advance you get, up to the maximum built into the distributor. These distributors are cheap and work OK with some engines and carb set-ups. However, they DO NOT work with stock 34 carbs. There are all kinds of "tricks" to make this combination work and I've tried 'em all . . . none of them work. The engine will run, but it will bog down every time you step on the gas.
The SVDA has both vaccuum and mechanical advances. The vacuum advance pulls the points plate to advance the timing as you step on the gas. The mechanical takes over and advances it even further as the engine speed increases.
As for how this is different than, lets say, a small block chevy . . . it's been way to many years since I worked on one. My best guess would be that if there is a difference, it may be due to manifold vacuum vs. venturi vacuum. Manifold vacuum will drop when you open the throttle plate opens due to the increased air flow into the manifold, but at the same time, venturi vacuum increases due to the increased air flow through the carb's venturi. The VW SVDA distributors use venturi vacuum.
