My distributor was curved by a pro shop and it is suppose to be all in by 3000rpm. Last year before Columbus, I checked timing it it was all in at about 3800. Since I had never tried to verify their work, I did not know if they may have made an error and it was like that from the beginning or something was wrong. The advance rate and amount was consistent so I didn't worry about it.
This past week, I decided to have a look. I found two things. One advance weight was loose and there was one huge spring. I couldn't really do anything about the weight so being the daredevil I am, I left it and swapped the huge spring for a much lighter one. The way the heavy spring was setup, it didn't come into play until the very end. So the lighter spring brought it all in by about 3600 but it was no longer being consistent. I then remembered that I had taken a distributor apart and had parts... somewhere. So about two hours later I found the parts.
The problem with the weight was the bushing. It's white, plastic of some kind and clips onto the post that the weight pivots on. Mine was no longer clipping it onto the post. The clearance seemed good but it was able to move up and down the post while in operation. I replaced it with a good spare and reinstalled everything. After that, it is all in at about 3000rpm and consistent. So my spring change probably had little to do with the end result and the weight was the problem.
You can see a bushing in this picture.
So when you're tuning one of these, make sure those bushings are in good condition. They don't seem to be available new but those distributors are very common so used bushings can be found pretty easily.
It feels quicker now and I'm also playing around with the accelerator pump so maybe I can find a little more.
While I was doing this, a friend was also tuning his Mopar. He uses a GM recurve kit for the springs. I didn't try them, but it looks like those springs would work and you get a much larger variety.