The 2 springs in the Mopar kit are way too light to use together, I got almost full advance at idle when I used both. Used one MP spring and the FBO light one in there. Advance starts just off idle and all in at 1700. The slots I set to .350" wide (mine were made adjustable) and that gave 13 degrees. My 440 likes this combo with initial at 24. Similar to what was mentioned in a previous post.

I had a stiffer spring in it before and advanced started at about 1500 or so. Problem was off idle - normal driving (auto trans) there was a slight bog or stumble until that advance came in and then it would take off and run good. Seemed like a carb problem - like the squirter, but I couldn't find it. Redid the advance so it starts moving right off idle, and that fixed it.