I broke my engine in today. I had the engine running at 2300 rpm. I set the timing at 28* with the vacuum advance unhooked. I noticed that occasionally the timing would advance way past the marks on the balanced just for a couple seconds and then return and stay there. That I saw it only happened a few times. I kept a constant watch on the timing for this reason while also watching everything else. What would cause an issue like that? I have had the distributor apart recently and installed a FBO limiter plate. Did I do something incorrectly when putting it back together. It seemed like a fairly simple procedure. I have MSD 6AL box and am using a basic timing light.