On this distributor the vacuum advance moves the plate inside the distributor. I found an old distributor with a vacuum advance and hooked it to the hose, and it works, moves the linkage. Hook the current va up and no movement when accelerating. So, I would say the current va has failed. Apparently to replace the va you have to take the dist housing out to replace the va. I wonder, can you buy just a va new for this dist.? Or, I could just use the old va I found. The linkage appears the same, but the dist is from an older truck.
