Vacuum advance issue

Cam1399 said
34 timing is 3400 rpm without advance in park. Runs great without the vacuum advance. I’ve hooked light up to it when I hood the vacuum advance up. As soon as I hit the throttle with the vacuum advance hooked up it starts pinging and the timing mark shoots off the light to the right. Timing at idle doesn’t change

Hang on a sec. Don't hit the throttle.
Tee a vacuum gauge into the Vacuum-advance line. Bring the rpm up slower and record the rpm when the vacuum advance signal hits a significant and repeatable number, like say 2 inches. If this happens at 900 rpm(in Neutral/park), that's crazy. If it happens closer to 1600 that would be closer to normal. If it takes a lotta throttle, the line may be plumbed to venturi vacuum which increases steadily with throttle opening and never drops to zero.
Also to-do, is to figure out how much timing your can is able to bring in, and how much vacuum it takes to do that.
The 11* at idle and 34* all in at 3400rpm is about right.You may be able to increase that just a tad, but what you have is a great start.