The vacuum piston is a vacuum retard system not advance like later cars.
The piston is pushed down on a retard ring on the advance weights , when the engine is started the vacuum pulls the piston upward againt spring tension allowing the advance to function normally.
when you accelerate the vac drops off allowing the piston again contact the ring retarding timing to prevent spark knock.
Many unhook the vac line and disable thinking this runs better , probably doesnt run better at all.
The piston also keeps the distributor in static time for starting as well and shouldnt be removed....
Car run good ??? leave it as is...........
