I wrote you earlier about your question. After playing around with some spare parts and testing each change, I have the solution to increasing the range of the mechanical advance on your HEI.
You can get more advance by modifying the shape of the fly weights. Here is the process:
You file down the fly weight straight inner surface that rubs against the center plate when the weights expand under rotation.
If you hold a weight in your fingers it kind of looks like the profile of a bird with a long beek. The surface you file is located on the lower part of the bird's beek. That's the straight surface that you file down.
The way to file the straight surface is to slightly taper the outer end and mid range, making the end of the bird's beek slightly more pointed. Be careful not to take too much off. It is amasing how little you have to remove to get the advance range to increase 10 degrees. You can check your progress if you have a spair HEI like I did. The fly weights are hard to file but you only need to taper the bird's beek a few degrees by removing a few thousanths of material.
I used # 106 fly weights but it does not matter what # you use. They all have the same profile, but their weights differ.
Warning: Do not mess with the center plates. I tried and it does not work. The various center plate numbers control the shape of the advance curve but not the range of advance. Changing plates will give you different rates of change (slopes) of the advance curve only.
I hope this works for you.
